Limit the number of services (NLSes, etc) that can be approved per user

Trying to activate additional packages/components will be silently rejected.

Bug: 428701593
Test: atest ManagedServicesTest NotificationManagerServiceTest
Flag: com.android.server.notification.limit_managed_services_count
Change-Id: Iddd8044997c41f97369b768f4da5e49efc43ad06