util: Use GlobSet in PathMatcher (#13197)

Previously we were using a single globset::Glob in PathMatcher; higher
up the stack, we were then resorting to using a list of PathMatchers.
globset crate exposes a GlobSet type that's better suited for this use
case. In my benchmarks, using a single PathMatcher with GlobSet instead
of a Vec of PathMatchers with Globs is about 3 times faster with the
default 'file_scan_exclusions' values. This slightly improves our
project load time for projects with large # of files, as showcased in
the following videos of loading a project with 100k source files. This
project is *not* a git repository, so it should measure raw overhead on
our side.

Current nightly: 51404d4ea0


https://github.com/zed-industries/zed/assets/24362066/e0aa9f8c-aae6-4348-8d42-d20bd41fcd76

versus this PR:


https://github.com/zed-industries/zed/assets/24362066/408dcab1-cee2-4c9e-a541-a31d14772dd7



Release Notes:

- Improved performance in large worktrees

crates/assistant/src/slash_command/diagnostics_command.rs

@@ -220,7 +220,7 @@ struct Options {
 const INCLUDE_WARNINGS_ARGUMENT: &str = "--include-warnings";
 
 impl Options {
-    pub fn parse(arguments_line: Option<&str>) -> Self {
+    fn parse(arguments_line: Option<&str>) -> Self {
         arguments_line
             .map(|arguments_line| {
                 let args = arguments_line.split_whitespace().collect::<Vec<_>>();
@@ -230,7 +230,7 @@ impl Options {
                     if arg == INCLUDE_WARNINGS_ARGUMENT {
                         include_warnings = true;
                     } else {
-                        path_matcher = PathMatcher::new(arg).log_err();
+                        path_matcher = PathMatcher::new(&[arg.to_owned()]).log_err();
                     }
                 }
                 Self {
@@ -255,7 +255,8 @@ fn collect_diagnostics(
     cx: &mut AppContext,
 ) -> Task<Result<(String, Vec<(Range<usize>, PlaceholderType)>)>> {
     let error_source = if let Some(path_matcher) = &options.path_matcher {
-        Some(path_matcher.source().to_string())
+        debug_assert_eq!(path_matcher.sources().len(), 1);
+        Some(path_matcher.sources().first().cloned().unwrap_or_default())
     } else {
         None
     };