Add API Service.getForegroundServiceType()

To return current foregroundServiceType if the service has become a
foreground service.

If service become foreground service by calling Service.startForeground(int,
Notification, int type), the returned type is the type specified.

If the no-type version Service.startForeground(int, Notification) is called.
the returned type is foregroundServiceType specified in manifest.

If no foregroundServiceType specified in manifest, the returned type is
zero.

If the service is not a foreground service, the returned type is zero.

Bug: 124517685
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerProcessStateTest.java#testFgsLocation

Change-Id: Ibcc4431429a90aab92a5533e296fb104b4add9e6