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/project/src/project.rs

@@ -5306,16 +5306,6 @@ impl ProjectItem for Buffer {
 }
 
 impl Completion {
-    pub fn filter_text(&self) -> &str {
-        match &self.source {
-            CompletionSource::Lsp { lsp_completion, .. } => lsp_completion
-                .filter_text
-                .as_deref()
-                .unwrap_or_else(|| self.label.filter_text()),
-            _ => self.label.filter_text(),
-        }
-    }
-
     pub fn kind(&self) -> Option<CompletionItemKind> {
         self.source
             // `lsp::CompletionListItemDefaults` has no `kind` field