Existing ContentObserver will cache values and overwrite
them when the value itself is modified or caller force
updates.
Bug: 149571513
Test: Wrote unit tests, mostly for caching logic.
Not meant to test ContentObserver contract for registering an
observer.
Change-Id: I12835f6c2be27ce17f65a55c51c4ef85c63b4487
This will reduce confusion with the other "badging" concept we use for,
e.g. work profiles. It is also consistent with the external name
"notification dots".
Change-Id: I2a2c9d96dc0d6284eb0c48adc78a856271caad4d