Allow background-restricted app to start FGS from alarm-clock.

Check FGS start temp allowlist reasonCode, with REASON_ALARM_MANAGER_ALARM_CLOCK,
the FGS can start even the app is background-restricted (With other reasonCode,
FGS can not start if the app is background-restricted).

With REASON_ALARM_MANAGER_ALARM_CLOCK, after FGS is started, if the app is changed to
background-restricted, the FGS can keep running (With other reasonCode, FGS
will be stopped if the app is changed to background-restricted).

Bug: 279233038
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java#testTempAllowListReasonCodeAlarmClock
atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java#testAlarmClockFgsNotStoppedByBackgroundRestricted

Change-Id: I909b15ba93735ff06787efc9c1e40c1c033a41ab