Blast: Populate compositor timings

Compositor timings are populated in BufferLayer::onPostComposition
but the callback handles were cleared before in
BufferStateLayer::releasePendingBuffer. Fix the ordering and add a
test.

Test: atest BLASTFrameEventHistoryTest
Fixes: 191247797
Change-Id: I5f93ed7f80cdcb4c0c6763fa37bad5e77588a20a