lsp colors: Reduce flickering while typing (#40055)

Closes #40019

Follow-up https://github.com/zed-industries/zed/pull/40025

This PR reduces/removes the flickering of inlay colors. This is done by
adding a debounce, and not detaching the task that fetches the new
colors.

**Result**


https://github.com/user-attachments/assets/5dae278b-b821-4e64-8adb-c4d8376ba1df

Release Notes:

- Lsp colors: Reduce flickering while typing.

---------

Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/collab/src/tests/editor_tests.rs

@@ -4,7 +4,7 @@ use crate::{
 };
 use call::ActiveCall;
 use editor::{
-    DocumentColorsRenderMode, Editor, RowInfo, SelectionEffects,
+    DocumentColorsRenderMode, Editor, FETCH_COLORS_DEBOUNCE_TIMEOUT, RowInfo, SelectionEffects,
     actions::{
         ConfirmCodeAction, ConfirmCompletion, ConfirmRename, ContextMenuFirst,
         ExpandMacroRecursively, MoveToEnd, Redo, Rename, SelectAll, ToggleCodeActions, Undo,
@@ -2409,6 +2409,7 @@ async fn test_lsp_document_color(cx_a: &mut TestAppContext, cx_b: &mut TestAppCo
         .unwrap();
 
     color_request_handle.next().await.unwrap();
+    executor.advance_clock(FETCH_COLORS_DEBOUNCE_TIMEOUT);
     executor.run_until_parked();
 
     assert_eq!(