Use LiveKit's Rust SDK on Linux while continue using Swift SDK on Mac (#21550)

Similar to #20826 but keeps the Swift implementation. There were quite a
few changes in the `call` crate, and so that code now has two variants.

Closes #13714

Release Notes:

- Added preliminary Linux support for voice chat and viewing
screenshares.

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/livekit_client_macos/src/livekit_client.rs

@@ -0,0 +1,37 @@
+#![allow(clippy::arc_with_non_send_sync)]
+
+use std::sync::Arc;
+
+#[cfg(all(target_os = "macos", not(any(test, feature = "test-support"))))]
+pub mod prod;
+
+#[cfg(all(target_os = "macos", not(any(test, feature = "test-support"))))]
+pub use prod::*;
+
+#[cfg(any(test, feature = "test-support", not(target_os = "macos")))]
+pub mod test;
+
+#[cfg(any(test, feature = "test-support", not(target_os = "macos")))]
+pub use test::*;
+
+pub type Sid = String;
+
+#[derive(Clone, Eq, PartialEq)]
+pub enum ConnectionState {
+    Disconnected,
+    Connected { url: String, token: String },
+}
+
+#[derive(Clone)]
+pub enum RoomUpdate {
+    ActiveSpeakersChanged { speakers: Vec<Sid> },
+    RemoteAudioTrackMuteChanged { track_id: Sid, muted: bool },
+    SubscribedToRemoteVideoTrack(Arc<RemoteVideoTrack>),
+    SubscribedToRemoteAudioTrack(Arc<RemoteAudioTrack>, Arc<RemoteTrackPublication>),
+    UnsubscribedFromRemoteVideoTrack { publisher_id: Sid, track_id: Sid },
+    UnsubscribedFromRemoteAudioTrack { publisher_id: Sid, track_id: Sid },
+    LocalAudioTrackPublished { publication: LocalTrackPublication },
+    LocalAudioTrackUnpublished { publication: LocalTrackPublication },
+    LocalVideoTrackPublished { publication: LocalTrackPublication },
+    LocalVideoTrackUnpublished { publication: LocalTrackPublication },
+}