editor: Utilize filter_text from language server for filter_range (#33155)

Closes #33106

Instead of directly using `filter_text` in `StringMatchCandidate`, which
yields better results for fuzzy matching but messes up with highlighting
letters in bold, as `positions` list generated by fuzzy crate are now of
`filter_text` and not `label` shown to the user.

This PR fixes it by keeping use of `filter_range` in
`StringMatchCandidate`, which is range w.r.t to `label` shown to user.
And actually generating this `filter_range` at source by using
`filter_range` if exists.

- [x] Tests

Release Notes:

- Fixed issue where incorrect letters are marked as bold in completions.

crates/editor/src/code_completion_tests.rs

@@ -264,11 +264,7 @@ impl CompletionBuilder {
         Completion {
             replace_range: Anchor::MIN..Anchor::MAX,
             new_text: label.to_string(),
-            label: CodeLabel {
-                text: label.to_string(),
-                runs: Default::default(),
-                filter_range: 0..label.len(),
-            },
+            label: CodeLabel::plain(label.to_string(), filter_text),
             documentation: None,
             source: CompletionSource::Lsp {
                 insert_range: None,
@@ -299,7 +295,7 @@ async fn filter_and_sort_matches(
     let candidates: Arc<[StringMatchCandidate]> = completions
         .iter()
         .enumerate()
-        .map(|(id, completion)| StringMatchCandidate::new(id, &completion.filter_text()))
+        .map(|(id, completion)| StringMatchCandidate::new(id, &completion.label.filter_text()))
         .collect();
     let cancel_flag = Arc::new(AtomicBool::new(false));
     let background_executor = cx.executor();