Adding a permission to protect exact alarms

Added a new permission to protect the alarm manager APIs setAlarmClock
and setExactAndAllowWhileIdle. The change will apply to apps targeting
API S and above.
- The permission will be granted by default to apps that request it.
- This will be a user facing permission as these APIs allow for exact
scheduling, and an app should generally only use them when scheduling
work on behalf of the user. This means the user can revoke it when they
want.
- Alarms set with this API will also be allowed to start FGS from the
background.
- Quota on exact, allow-while-idle alarms has been relaxed generously,
while alarm-clocks remain totally uninhibited.
- Apps that are exempted from battery via <allow-in-power-save> in the
sysconfig, can still use exact, allow-while-idle alarms without the
permission, but with lower quota.
- Inexact, allow-while-idle alarms do not require this permission, but
will *not* be allowed to start FGS from the background.
- A new API to query the state of this permission is included.

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

BYPASS_INCLUSIVE_LANGUAGE_REASON=Existing APIs

Bug: 171306433
Change-Id: Ifb6a3f3c42316b1c83fe6960920501f5e0ee51f2