Exempting prioritized alarms from min_window

Prioritized alarms are already protected quite tightly, and they rely on
a listener. So they are allowed to choose their window freely.

Reshuffled the permission and parameter checks to be simpler.

Test: atest CtsAlarmManagerTestCases
atest FrameworksMockingServicesTests:com.android.server.alarm

Bug: 185199076
Change-Id: Ia86541c61202e8c82cb810fedfb83a47118b0b02