Clear mSyncGroups when VRI does a performTraversal

When VRI is ready to start drawing, we need to sync any SV syncs
that have started, but not completed yet. However, it's possible a
second VRI can start drawing before the SV completes which would include
those original SV syncs in the second VRI frame. This isn't the expected
behavior since each SV sync is intended for a single VRI frame.
Therefore, clear the saved SV syncGroups once VRI is expected to start
drawing.

Test: async SV with resize due to insets no longer ANRs.
Bug: 263340543
Change-Id: Ib37505cd494ced68a7d9db291fe42d786d900a8a