Adjust "services.core" defaults for Error Prone.

It ends up that "services.core" itself doesn't catch Error Prone
issues, since it works with JAR output from a previous stage.  To
resolve this, we need to move up to "services.core.unboosted" where
the source code is still available.

Fix one instance of AndroidFrameworkCompatChange that had leaked
into the source tree recently.  Disable other checks since there
are hundreds of failures inside the actual "services.core" code.

Bug: 155703208
Test: manual
Exempt-From-Owner-Approval: trivial refactoring
Change-Id: I13f15db61bbcf5f74023147a95551b541d0a8845