start.zig: Replace kernel32 usage with ntdll/PEB

[squeek502]

Credit to @e4m2 for identifying which ntdll functions/PEB fields could be used to replace the kernel32 functions (#17763 (comment)). Progress towards #1840

Functionality is equivalent before and after:

Test code:

winmain-zig.zig:

const std = @import("std");

pub fn wWinMain(
    inst: std.os.windows.HINSTANCE,
    prev: ?std.os.windows.HINSTANCE,
    cmd_line: std.os.windows.LPWSTR,
    cmd_show: i32,
) std.os.windows.INT {
    std.debug.print("inst: {}\n", .{inst});
    std.debug.print("prev: {?}\n", .{prev});
    const cmd_line_slice = std.mem.span(cmd_line);
    std.debug.print("cmd_line: {}\n", .{std.unicode.fmtUtf16le(cmd_line_slice)});
    std.debug.print("cmd_show: {}\n", .{cmd_show});
    return 0;
}

Before:

> winmain-zig-kernel32.exe a b c "кириллица"
inst: os.windows.HINSTANCE__opaque_2599@7ff62c1f0000
prev: null
cmd_line: winmain-zig-kernel32.exe  a b c "кириллица"
cmd_show: 10

NtTrace of how the process is terminated:

NtTerminateProcess( ProcessHandle=0, ExitStatus=0 ) => 0
NtClose( Handle=0x78 ) => 0
NtClose( Handle=0x50 ) => 0
NtClose( Handle=0x70 ) => 0
NtClose( Handle=0x74 ) => 0
Process 15996 exit code: 0

After:

> winmain-zig-ntdll.exe a b c "кириллица"
inst: os.windows.HINSTANCE__opaque_2614@7ff6dc490000
prev: null
cmd_line: winmain-zig-ntdll.exe  a b c "кириллица"
cmd_show: 10

NtTrace:

NtTerminateProcess( ProcessHandle=0, ExitStatus=0 ) => 0
NtClose( Handle=0x78 ) => 0
NtClose( Handle=0x60 ) => 0
NtClose( Handle=0x70 ) => 0
NtClose( Handle=0x74 ) => 0
Process 23044 exit code: 0