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/languages/src/python.rs

@@ -268,10 +268,15 @@ impl LspAdapter for PythonLspAdapter {
             lsp::CompletionItemKind::CONSTANT => grammar.highlight_id_for_name("constant")?,
             _ => return None,
         };
+        let filter_range = item
+            .filter_text
+            .as_deref()
+            .and_then(|filter| label.find(filter).map(|ix| ix..ix + filter.len()))
+            .unwrap_or(0..label.len());
         Some(language::CodeLabel {
             text: label.clone(),
             runs: vec![(0..label.len(), highlight_id)],
-            filter_range: 0..label.len(),
+            filter_range,
         })
     }
 
@@ -1152,10 +1157,15 @@ impl LspAdapter for PyLspAdapter {
             lsp::CompletionItemKind::CONSTANT => grammar.highlight_id_for_name("constant")?,
             _ => return None,
         };
+        let filter_range = item
+            .filter_text
+            .as_deref()
+            .and_then(|filter| label.find(filter).map(|ix| ix..ix + filter.len()))
+            .unwrap_or(0..label.len());
         Some(language::CodeLabel {
             text: label.clone(),
             runs: vec![(0..label.len(), highlight_id)],
-            filter_range: 0..label.len(),
+            filter_range,
         })
     }