gen_rust_project: optimize aquery with many targets (#2941)

Hi, if I'm not mistaken, in Bazel `deps(a)+deps(b)` is equivalent to
`deps(a+b)`. The latter is more efficient because it doesn't have to
deduplicate common dependencies between a and b. This performance issue
has been triggered in our configuration, as we track roughly 700 targets
and 1600 transitive dependencies in our monorepo.
Running `aquery` with the original implementation takes 15 seconds on my
machine while the implementation proposed in this PR takes 1.5 seconds.

tools/rust_analyzer/aquery.rs

@@ -69,11 +69,7 @@ pub fn get_crate_specs(
     rules_rust_name: &str,
 ) -> anyhow::Result<BTreeSet<CrateSpec>> {
     log::debug!("Get crate specs with targets: {:?}", targets);
-    let target_pattern = targets
-        .iter()
-        .map(|t| format!("deps({t})"))
-        .collect::<Vec<_>>()
-        .join("+");
+    let target_pattern = format!("deps({})", targets.join("+"));
 
     let aquery_output = Command::new(bazel)
         .current_dir(workspace)