Refactor SurfaceSyncer to use SurfaceSyncGroups instead of syncId

There's no need for SurfaceSyncer to store the SyncSets and only return
a syncId. The callers can instead own the SyncGroups and call methods
directly on them. This makes the code more readable and cleans up Syncer
since you can directly call methods instead of piping through an outer
method.

Test: SurfaceSyncGroupContinuousTest
Test: SurfaceSyncGroupTest
Change-Id: I82976e26e10e20d2752e6be24a45069a6a64e849
Bug: 237804605