Add SurfaceSyncer class

Add Syncer class that allows callers to add desired syncs into a set and
wait for them to all complete before getting a callback. The purpose of
the Syncer is to be an accounting mechanism so each sync implementation
doesn't need to handle it themselves. The Syncer class is used the
following way.

1. SurfaceSyncer#setupSync is called
2. addToSync is called for every SyncTarget object that wants to be
   included in the sync. If the addSync is called for a View or
   SurfaceView it needs to be called on the UI thread. When addToSync is
   called, it's guaranteed that any UI updates that were requested before
   addToSync but after the last frame drew, will be included in the sync.
3. SurfaceSyncer#markSyncReady should be called when all the SyncTargets
   have been added to the SyncSet. Now the SyncSet is closed and no more
   SyncTargets can be added to it.
4. When all SyncTargets are complete, the final merged Transaction will
   either be applied or sent back to the caller.

The following is what happens within the SyncSet
1. Each SyncableTarget will get an onReadyToSync callback that contains
   a SyncBufferCallback.
2. Each SyncableTarget needs to invoke SyncBufferCallback#onBufferReady.
   This makes sure the SyncSet knows when the SyncTarget is complete,
   allowing the SyncSet to get the Transaction that contains the buffer.
3. When the final FrameCallback finishes for the SyncSet, the
   syncRequestComplete Consumer will be invoked with the transaction
   that contains all information requested in the sync. This could include
   buffers and geometry changes. The buffer update will include the UI
   changes that were requested for the View.

Test: SurfaceSyncerTest
Test: SurfaceSyncerContinuousTest
Bug: 200284684
Change-Id: Iab87bff8a0483581e57803724eae88f0a3d96c8e