fix(data-tracks): adapt to split UniFFI signal handler API

Upstream livekit-uniffi replaced the generic `handleSignalResponse`
with specific per-message handlers:
- handleSfuRequestResponse (for RequestResponse)
- handleSfuPublishResponse (for PublishDataTrackResponse)
- handleSfuParticipantUpdate (for ParticipantUpdate)
- handleSubscriberHandles (for DataTrackSubscriberHandles)

Each handler returns UnsupportedType for messages it doesn't handle,
so the simplest integration is to call all four with the raw bytes
and let them filter internally.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pblazej

Sources/LiveKit/Core/Room+SignalClientDelegate.swift

@@ -407,9 +407,13 @@ extension Room: SignalClientDelegate {
     }
 
     func signalClient(_: SignalClient, didReceiveRawResponse data: Data) async {
-        try? localDataTrackManager?.handleSignalResponse(res: data)
+        // Each manager has specific handler methods per message type.
+        // Try them all — they return UnsupportedType for messages they don't handle.
+        try? localDataTrackManager?.handleSfuRequestResponse(res: data)
+        try? localDataTrackManager?.handleSfuPublishResponse(res: data)
+        try? remoteDataTrackManager?.handleSubscriberHandles(res: data)
         if let identity = localParticipant.identity?.stringValue {
-            try? remoteDataTrackManager?.handleSignalResponse(
+            try? remoteDataTrackManager?.handleSfuParticipantUpdate(
                 res: data,
                 localParticipantIdentity: identity
             )