audio: Run webrtc receiver task on the realtime-priority thread as well (#51315)

Co-authored-by: Jakub Konka <jakub@zed.dev>

Closes #ISSUE

Before you mark this PR as ready for review, make sure that you have:
- [ ] Added a solid test coverage and/or screenshots from doing manual
testing
- [ ] Done a self-review taking into account security and performance
aspects
- [ ] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)

Release Notes:

- Fixed issues with tremendous audio latency in long-running collab
calls.

Co-authored-by: Jakub Konka <jakub@zed.dev>

crates/livekit_client/src/livekit_client/playback.rs

@@ -111,7 +111,7 @@ impl AudioStack {
             source.num_channels as i32,
         );
 
-        let receive_task = self.executor.spawn({
+        let receive_task = self.executor.spawn_with_priority(Priority::RealtimeAudio, {
             let source = source.clone();
             async move {
                 while let Some(frame) = stream.next().await {
@@ -202,7 +202,7 @@ impl AudioStack {
         let apm = self.apm.clone();
 
         let (frame_tx, mut frame_rx) = futures::channel::mpsc::unbounded();
-        let transmit_task = self.executor.spawn({
+        let transmit_task = self.executor.spawn_with_priority(Priority::RealtimeAudio, {
             async move {
                 while let Some(frame) = frame_rx.next().await {
                     source.capture_frame(&frame).await.log_err();