Improve LSP tasks ergonomics (#31551)

* stopped fetching LSP tasks for too long (but still use the hardcoded
value for the time being — the LSP tasks settings part is a simple bool
key and it's not very simple to fit in another value there)

* introduced `prefer_lsp` language task settings value, to control
whether in the gutter/modal/both/none LSP tasks are shown exclusively,
if possible

Release Notes:

- Added a way to prefer LSP tasks over Zed tasks

crates/editor/src/editor_tests.rs

@@ -9111,11 +9111,10 @@ async fn test_range_format_during_save(cx: &mut TestAppContext) {
                 lsp::Url::from_file_path(path!("/file.rs")).unwrap()
             );
             assert_eq!(params.options.tab_size, 8);
-            Ok(Some(vec![]))
+            Ok(Some(Vec::new()))
         })
         .next()
         .await;
-    cx.executor().start_waiting();
     save.await;
 }