AudioFlinger: Use std::any for the event cookie

This generalizes over the previous wp<RefBase> cookie.

Test: atest mediasyncevent_tests
Test: atest synchronizedrecordstate_tests
Test: atest MediaSyncEventTest
Bug: 288339104
Bug: 288943829
Change-Id: Iaa535450550681517613310a7043526be38c2aae
4 files changed