AudioFlinger: Refactor SyncEvent

Extract SyncEvent code as is to separate file.

Test: atest MediaSyncEventTest
Bug: 283021652
Change-Id: I2212cdc52513f49b08e0383f26548f6dbda4741c
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 5fcc302..71ce426 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -4001,7 +4001,7 @@
     track->setTeePatchesToUpdate(std::move(teePatches));
 }
 
-sp<AudioFlinger::SyncEvent> AudioFlinger::createSyncEvent(AudioSystem::sync_event_t type,
+sp<SyncEvent> AudioFlinger::createSyncEvent(AudioSystem::sync_event_t type,
                                     audio_session_t triggerSession,
                                     audio_session_t listenerSession,
                                     sync_event_callback_t callBack,