Improve updateInputFlinger performance

This change improves the performance of the WindowInfosListenerInvoker work done on SurfaceFlinger's background executor thread. The primary optimization made is not sending a WindowInfosReportedListener with every call to WindowInfosListener.onWindowInfosChanged. Instead, we send a new interface, WindowInfosPublisher, and a unique listener id to listeners when they're added.  Listeners call WindowInfosPublisher.ackWindowInfosReceived with their id after processing each update.

From traces taken during development, the new code is a major improvement, taking about 15% of the time spent previously on SurfaceFlinger's background thread for sending window infos. Performance with this change seems roughly in line with the performance in T.

Bug: 290377931
Test: atest WindowInfosListenerTest
Test: atest WindowInfosListenerInvokerTest
Test: manually killing system server and checking valid state on restart
Change-Id: Ib39ba935727df0bc1ab4030bcfe8301de7e64805
diff --git a/services/surfaceflinger/BackgroundExecutor.h b/services/surfaceflinger/BackgroundExecutor.h
index 0fae5a5..66b7d7a 100644
--- a/services/surfaceflinger/BackgroundExecutor.h
+++ b/services/surfaceflinger/BackgroundExecutor.h
@@ -34,6 +34,7 @@
     // Queues callbacks onto a work queue to be executed by a background thread.
     // This is safe to call from multiple threads.
     void sendCallbacks(Callbacks&& tasks);
+    void flushQueue();
 
 private:
     sem_t mSemaphore;