package: filter unpack errors for excluded files

Before this any unpack error will be raised after the unpack step. Now
this is postponed until we get manifest, and if then use included
folders from manifest to filter errors which are not for the files from
included folders.

I made a folder which has symlinks and file names with same names in
different casing.
```
sample
├── build.zig
├── build.zig.zon
├── dir1
│   └── dir2
│       └── dir3
│           ├── file1
│           ├── file2
│           └── file3
├── dir4
│   └── dir5
│       └── dir6
│           ├── file1 -> ../../../dir1/dir2/dir3/file1
│           └── file2_symlink -> ../../../dir1/dir2/dir3/file2
├── dir7
│   └── dir8
│       └── dir9
│           ├── file4
│           └── File4
└── src
    ├── main.zig
    └── root.zig
```

Then pack this into sample.tar and another one sample_src.tar where
build.zig.zon has only src in paths (excluded all problematic folders):
```Zig
    .paths = .{
        "src",
    },
```

On Linux both tars get unpacked. On Windows and macOS both fail before
this changes and second succeds after this change.

Windows (with disabled symlinks):
```
C:\Users\ianic\code\zig-bin\zig.exe build --global-cache-dir zig-global-cache-release
C:\Users\ianic\code\issues\fetch\build.zig.zon:78:20: error: unable to unpack tarball
            .url = "http://10.211.55.26:8000/sample.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: unable to create file 'dir7/dir8/dir9/file4': PathAlreadyExists
note: unable to create symlink from 'dir4/dir5/dir6/file1' to '../../../dir1/dir2/dir3/file1': AccessDenied
note: unable to create symlink from 'dir4/dir5/dir6/file2_symlink' to '../../../dir1/dir2/dir3/file2': AccessDenied
C:\Users\ianic\code\issues\fetch\build.zig.zon:85:20: error: unable to unpack tarball
            .url = "http://10.211.55.26:8000/sample_src.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: unable to create file 'dir7/dir8/dir9/file4': PathAlreadyExists
note: unable to create symlink from 'dir4/dir5/dir6/file1' to '../../../dir1/dir2/dir3/file1': AccessDenied
note: unable to create symlink from 'dir4/dir5/dir6/file2_symlink' to '../../../dir1/dir2/dir3/file2': AccessDenied
PS C:\Users\ianic\code\issues\fetch> C:\Users\ianic\code\zig-bin\bin\zig.exe build --global-cache-dir zig-global-cache-release

C:\Users\ianic\code\zig-io\build\stage3\bin\zig.exe build --global-cache-dir zig-global-cache-master
C:\Users\ianic\code\issues\fetch\build.zig.zon:78:20: error: unable to unpack
            .url = "http://10.211.55.26:8000/sample.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: unable to create file 'dir7/dir8/dir9/file4': PathAlreadyExists
note: unable to create symlink from 'dir4/dir5/dir6/file1' to '../../../dir1/dir2/dir3/file1': AccessDenied
note: unable to create symlink from 'dir4/dir5/dir6/file2_symlink' to '../../../dir1/dir2/dir3/file2': AccessDenied
```

macOS
```
Fetch Packages [45/40] /Users/ianic/code/zig/issues/fetch/build.zig.zon:75:20: error: unable to unpack tarball
            .url = "file:///Users/ianic/code/zig/issues/fetch/sample.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: unable to create file 'dir7/dir8/dir9/file4': PathAlreadyExists
/Users/ianic/code/zig/issues/fetch/build.zig.zon:80:20: error: unable to unpack tarball
            .url = "file:///Users/ianic/code/zig/issues/fetch/sample_src.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fetch Packages [41/40] /Users/ianic/code/zig/issues/fetch/build.zig.zon:75:20: error: unable to unpack
            .url = "file:///Users/ianic/code/zig/issues/fetch/sample.tar",
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
note: unable to create file 'dir7/dir8/dir9/file4': PathAlreadyExists

```

Author: ianic

src/Package/Fetch.zig

@@ -461,7 +461,8 @@ fn runResource(
         };
         defer tmp_directory.handle.close();
 
-        try unpackResource(f, resource, uri_path, tmp_directory);
+        var errors = try unpackResource(f, resource, uri_path, tmp_directory);
+        defer errors.deinit();
 
         // Load, parse, and validate the unpacked build.zig.zon file. It is allowed
         // for the file to be missing, in which case this fetched package is
@@ -479,6 +480,9 @@ fn runResource(
             .include_paths = if (f.manifest) |m| m.paths else .{},
         };
 
+        try errors.remove(filter);
+        try f.emitUnpackErrors(&errors);
+
         // Compute the package hash based on the remaining files in the temporary
         // directory.
 
@@ -1032,7 +1036,7 @@ fn unpackResource(
     resource: *Resource,
     uri_path: []const u8,
     tmp_directory: Cache.Directory,
-) RunError!void {
+) RunError!Unpack.Errors {
     const eb = &f.error_bundle;
     const file_type = switch (resource.*) {
         .file => FileType.fromPath(uri_path) orelse
@@ -1096,15 +1100,15 @@ fn unpackResource(
         .dir => |dir| return try f.recursiveDirectoryCopy(dir, tmp_directory.handle, uri_path),
     };
 
-    switch (file_type) {
+    return switch (file_type) {
         .tar => try unpackTarball(f, tmp_directory.handle, resource.reader()),
-        .@"tar.gz" => {
+        .@"tar.gz" => brk: {
             const reader = resource.reader();
             var br = std.io.bufferedReaderSize(std.crypto.tls.max_ciphertext_record_len, reader);
             var dcp = std.compress.gzip.decompressor(br.reader());
-            try unpackTarball(f, tmp_directory.handle, dcp.reader());
+            break :brk try unpackTarball(f, tmp_directory.handle, dcp.reader());
         },
-        .@"tar.xz" => {
+        .@"tar.xz" => brk: {
             const gpa = f.arena.child_allocator;
             const reader = resource.reader();
             var br = std.io.bufferedReaderSize(std.crypto.tls.max_ciphertext_record_len, reader);
@@ -1115,38 +1119,36 @@ fn unpackResource(
                 ));
             };
             defer dcp.deinit();
-            try unpackTarball(f, tmp_directory.handle, dcp.reader());
+            break :brk try unpackTarball(f, tmp_directory.handle, dcp.reader());
         },
-        .@"tar.zst" => {
+        .@"tar.zst" => brk: {
             const window_size = std.compress.zstd.DecompressorOptions.default_window_buffer_len;
             const window_buffer = try f.arena.allocator().create([window_size]u8);
             const reader = resource.reader();
             var br = std.io.bufferedReaderSize(std.crypto.tls.max_ciphertext_record_len, reader);
             var dcp = std.compress.zstd.decompressor(br.reader(), .{
                 .window_buffer = window_buffer,
             });
-            return unpackTarball(f, tmp_directory.handle, dcp.reader());
+            break :brk try unpackTarball(f, tmp_directory.handle, dcp.reader());
         },
         .git_pack => try unpackGitPack(f, tmp_directory.handle, resource),
-    }
+    };
 }
 
 const Unpack = @import("Unpack.zig");
 
-fn unpackTarball(f: *Fetch, out_dir: fs.Dir, reader: anytype) RunError!void {
+fn unpackTarball(f: *Fetch, out_dir: fs.Dir, reader: anytype) RunError!Unpack.Errors {
     var unpack = Unpack.init(f.arena.child_allocator, out_dir);
-    defer unpack.deinit();
     unpack.tarball(reader) catch |err| return f.failMsg(
         err,
         "unable to unpack tarball to temporary directory: {s}",
         .{@errorName(err)},
     );
-    try f.checkUnpackErrors(&unpack);
+    return unpack.errors;
 }
 
-fn unpackGitPack(f: *Fetch, out_dir: fs.Dir, resource: *Resource) RunError!void {
+fn unpackGitPack(f: *Fetch, out_dir: fs.Dir, resource: *Resource) RunError!Unpack.Errors {
     var unpack = Unpack.init(f.arena.child_allocator, out_dir);
-    defer unpack.deinit();
 
     const want_oid = resource.git.want_oid;
     const reader = resource.git.fetch_stream.reader();
@@ -1155,18 +1157,17 @@ fn unpackGitPack(f: *Fetch, out_dir: fs.Dir, resource: *Resource) RunError!void
         "unable to unpack git files: {s}",
         .{@errorName(err)},
     );
-    try f.checkUnpackErrors(&unpack);
+    return unpack.errors;
 }
 
-fn recursiveDirectoryCopy(f: *Fetch, dir: fs.Dir, out_dir: fs.Dir, uri_path: []const u8) RunError!void {
+fn recursiveDirectoryCopy(f: *Fetch, dir: fs.Dir, out_dir: fs.Dir, uri_path: []const u8) RunError!Unpack.Errors {
     var unpack = Unpack.init(f.arena.child_allocator, out_dir);
-    defer unpack.deinit();
     unpack.directory(dir) catch |err| return f.failMsg(
         err,
         "unable to copy directory '{s}': {s}",
         .{ uri_path, @errorName(err) },
     );
-    try f.checkUnpackErrors(&unpack);
+    return unpack.errors;
 }
 
 fn failMsg(f: *Fetch, err: anyerror, comptime fmt: []const u8, args: anytype) RunError {
@@ -1177,18 +1178,18 @@ fn failMsg(f: *Fetch, err: anyerror, comptime fmt: []const u8, args: anytype) Ru
     }
 }
 
-fn checkUnpackErrors(f: *Fetch, unpack: *Unpack) RunError!void {
-    if (!unpack.hasErrors()) return;
+fn emitUnpackErrors(f: *Fetch, errors: *Unpack.Errors) RunError!void {
+    if (errors.count() == 0) return;
 
     const eb = &f.error_bundle;
-    const notes_len: u32 = @intCast(unpack.errors.items.len);
+    const notes_len: u32 = @intCast(errors.count());
     try eb.addRootErrorMessage(.{
         .msg = try eb.addString("unable to unpack"),
         .src_loc = try f.srcLoc(f.location_tok),
         .notes_len = notes_len,
     });
     const notes_start = try eb.reserveNotes(notes_len);
-    for (unpack.errors.items, notes_start..) |item, note_i| {
+    for (errors.list.items, notes_start..) |item, note_i| {
         switch (item) {
             .unable_to_create_sym_link => |info| {
                 eb.extra.items[note_i] = @intFromEnum(try eb.addErrorMessage(.{