Add listener on carrier privileged app changes for exempted FGS type

In case the carrier privileged app is changed, i.e. sim swap,
the new carrier privileged apps could start FGS with the
systemExempted type.

MUST_SLEEP

Bug: 275718387
Test: atest BackgroundRestrictionTest
Change-Id: Ia938da9669e8b447c9c9d93a7145c0d0f050eb08