Switch to use RefactoredBackupManagerService

Keeping the legacy BackupManagerService for now, but we'll remove
it in a few weeks if there's no issues noticed.
In case of any problems, this CL can be cleanly reverted as a fallback.

Test: pretty much all we got in store
1) runtest -p com.android.server.backup frameworks-services
2) make gts -j40 && gts-tradefed run gts -m GtsBackupHostTestCases
3) make cts -j40 && cts-tradefed run cts -m CtsBackupTestCases
4) make pts -j40 && pts-tradefed run pts -m PtsBackupHostSideTestCases
5) manual: "adb shell bmgr backupnow --all" and then cloud restore,
   D2D scenarios (both as source and target)
Bug: 65823538
Change-Id: I701764995c4fe2611a4941aecb45315aa457658e