Handle rollback from unified sqlite to xml

We aren't moving enable_sqlite_appops_accesses flag forward, and
will be using enable_all_sqlite_appops_accesses (unified schema)
for sqlite in nextfood. If we need to rollback, the rollback should
move data from unified schema sqlite to xml directly.

This CL also cleans up historical ops data during migration
or rollback.

Bug: 377584611
Test: presubmit
Test: DiscreteOpsMigrationAndRollbackTest
Test: manual
Flag: android.permission.flags.enable_all_sqlite_appops_accesses
Change-Id: I4a73fe281871b6652a88d239423f1f1197de8ed8