Make PermPolicySvc based on uid

Permissions and perm related appops are all based on uids. Hence this
service should use uids as it's main abstraction.

This also allows us to duplicate two ops-change requests for the same
uid.

Test: atest --test-mapping services/core/java/com/android/server/policy/PermissionPolicyService.java
Bug: 143918240
Change-Id: Ie1137d15b76c6b0d963b0987d5e806f76c142998