Only allow rollback to be enabled on modules.

Only allow rollback to be enabled on the modules included in a mainline
update. We don't want to support rollbacks for all apks in general yet.

Enforce that only installers granted the MANAGE_ROLLBACKS permission can
enable rollback for a package.

Introduce a new TEST_MANAGE_ROLLBACKS permission that can be used to
enable rollback on packages that are not modules. This allows us to
continue testing rollbacks, given we can't do a mainline update as part
of the rollback tests.

Test: atest RollbackTest, with new tests for permissions added.
Bug: 128277794
Change-Id: I29ab9a750a1283592b8a855322ece516e42260ca