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_context_menus.rs

@@ -260,7 +260,7 @@ impl CompletionsMenu {
         let match_candidates = completions
             .iter()
             .enumerate()
-            .map(|(id, completion)| StringMatchCandidate::new(id, completion.filter_text()))
+            .map(|(id, completion)| StringMatchCandidate::new(id, completion.label.filter_text()))
             .collect();
 
         let completions_menu = Self {
@@ -1115,7 +1115,7 @@ impl CompletionsMenu {
                     SnippetSortOrder::Inline => Reverse(0),
                 };
                 let sort_positions = string_match.positions.clone();
-                let sort_exact = Reverse(if Some(completion.filter_text()) == query {
+                let sort_exact = Reverse(if Some(completion.label.filter_text()) == query {
                     1
                 } else {
                     0