SF: Fix synthetic VSYNC after first powering on

After onActiveDisplayChangedLocked, isActiveDisplay was stale, so the
first powering on of a newly active display did not enable and resync
to hardware VSYNC, i.e. EventThread stayed in SyntheticVsync.

Also, merge EventThread APIs to enable/disable synthetic VSYNC.

Fixes: 264700488
Bug: 255635821
Test: dumpsys SurfaceFlinger --events
Change-Id: Ibd4099bb856adc11d887f3b7b9432fbc4cb2e33d
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index a340919..67f4daa 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -157,8 +157,8 @@
     void onHotplugReceived(ConnectionHandle, PhysicalDisplayId, bool connected);
     void onPrimaryDisplayModeChanged(ConnectionHandle, const FrameRateMode&) EXCLUDES(mPolicyLock);
     void onNonPrimaryDisplayModeChanged(ConnectionHandle, const FrameRateMode&);
-    void onScreenAcquired(ConnectionHandle);
-    void onScreenReleased(ConnectionHandle);
+
+    void enableSyntheticVsync(bool = true) REQUIRES(kMainThreadContext);
 
     void onFrameRateOverridesChanged(ConnectionHandle, PhysicalDisplayId)
             EXCLUDES(mConnectionsLock);