Expire rollback when apex is updated.

RollbackManager relies on package changed broadcasts to expire rollbacks
when an application is updated, but we don't receive package changed
broadcasts for apex.

This change adds an extra check when starting RollbackManager to see if
any apex versions have changed and expires rollbacks as appropriate.

Adds a test case to cover the scenario and refactors the test code
to properly set up the test apex in all cases with minimal reboots.

Bug: 126358044
Test: atest StagedRollbackTest, with new test added.
Change-Id: I7ea4953e4aff8d1c7560d6c61e6be5e4e8e1f194