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/editor/src/editor.rs

@@ -226,6 +226,7 @@ pub const SELECTION_HIGHLIGHT_DEBOUNCE_TIMEOUT: Duration = Duration::from_millis
 pub(crate) const CODE_ACTION_TIMEOUT: Duration = Duration::from_secs(5);
 pub(crate) const FORMAT_TIMEOUT: Duration = Duration::from_secs(5);
 pub(crate) const SCROLL_CENTER_TOP_BOTTOM_DEBOUNCE_TIMEOUT: Duration = Duration::from_secs(1);
+pub const FETCH_COLORS_DEBOUNCE_TIMEOUT: Duration = Duration::from_millis(150);
 
 pub(crate) const EDIT_PREDICTION_KEY_CONTEXT: &str = "edit_prediction";
 pub(crate) const EDIT_PREDICTION_CONFLICT_KEY_CONTEXT: &str = "edit_prediction_conflict";
@@ -1189,6 +1190,7 @@ pub struct Editor {
     inline_value_cache: InlineValueCache,
     selection_drag_state: SelectionDragState,
     colors: Option<LspColorData>,
+    refresh_colors_task: Task<()>,
     folding_newlines: Task<()>,
     pub lookup_key: Option<Box<dyn Any + Send + Sync>>,
 }
@@ -2244,6 +2246,7 @@ impl Editor {
             tasks_update_task: None,
             pull_diagnostics_task: Task::ready(()),
             colors: None,
+            refresh_colors_task: Task::ready(()),
             next_color_inlay_id: 0,
             linked_edit_ranges: Default::default(),
             in_project_search: false,