Fix some issues with branch buffers (#18945)

* `Open Excerpts` command always opens the locations in the base buffer
* LSP features like document-highlights, go-to-def, and inlay hints work
correctly in branch buffers
* Other LSP features like completions, code actions, and rename are
disabled in branch buffers

Release Notes:

- N/A

crates/remote_server/src/remote_editing_tests.rs

@@ -434,7 +434,7 @@ async fn test_remote_lsp(cx: &mut TestAppContext, server_cx: &mut TestAppContext
 
     project
         .update(cx, |project, cx| {
-            project.perform_rename(buffer.clone(), 3, "two".to_string(), true, cx)
+            project.perform_rename(buffer.clone(), 3, "two".to_string(), cx)
         })
         .await
         .unwrap();