Make cargo run always available for binaries

Previously, items for `cargo test` and `cargo check` would appear as in
the `Select Runnable` quick pick that appears when running
`rust-analyzer: Run`, but `run` would only appear as a runnable if a
`main`` function was selected in the editor. This change adds `cargo
run` as an always available runnable command for binary packages.

This makes it easier to develop cli / tui applications, as now users can
run application from anywhere in their codebase.

Author: joshka

crates/rust-analyzer/src/handlers/request.rs

@@ -836,10 +836,13 @@ pub(crate) fn handle_runnables(
     let config = snap.config.runnables();
     match cargo_spec {
         Some(spec) => {
-            let all_targets = !snap.analysis.is_crate_no_std(spec.crate_id)?;
-            for cmd in ["check", "test"] {
+            for cmd in ["check", "run", "test"] {
+                if cmd == "run" && spec.target_kind != TargetKind::Bin {
+                    continue;
+                }
                 let mut cargo_args =
                     vec![cmd.to_owned(), "--package".to_owned(), spec.package.clone()];
+                let all_targets = cmd != "run" && !snap.analysis.is_crate_no_std(spec.crate_id)?;
                 if all_targets {
                     cargo_args.push("--all-targets".to_owned());
                 }