Move AppInfo mock to FakeContext

Mockito occasionally complains due to some odd behavior related
to mocking calls in FakeContext (which is a spy(Context)). We
address this by implementing the function in FakeContext instead of
trying to mock it out later.

Fixes: 80431912
Test: atest CarrierServiceStateTrackerTest.java
Change-Id: I18385d84b85960efc51ea974c275ff6cfbf5cca5
Merged-In: I18385d84b85960efc51ea974c275ff6cfbf5cca5