[ADI][14/N] enable verifier on multi-user

We cannot guarantee that the verifier service has singleUser=true. If
the service is not intended to be singleUser, we must make sure that the
service on one user doesn't affect the service on another.

FLAG: android.content.pm.verification_service
BUG:  360129657
Test: more tests to be added
Test: manually with the demo verifier app with user switching

Merged-In: I855fa867f04af4e979f5bc8b7d45373b6d424be9
Change-Id: I855fa867f04af4e979f5bc8b7d45373b6d424be9