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
(cherry picked from commit a132684a093d9e1750100b39d4e4168f2d27d349)
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:182548fd95b0f245385e5dc45efd2cbd4cd35b57
Merged-In: Iddd8044997c41f97369b768f4da5e49efc43ad06
Change-Id: Iddd8044997c41f97369b768f4da5e49efc43ad06