Introduce monitoring behavior changes for USI devices (1/n)

- Whether the USI battery state is valid will depend on when we last got
  a battery state update. This means that battery for USI devices must
  always be monitored so that we know whether the state is valid when
  the first listener is registered. We add the concept of a perpetual
  monitor that is added at boot and never removed.
- Since USI battery state changes are always accompanied by UEvents,
  there is no need to poll for battery changes. Make sure that we don't
  poll for battery changes if we're only listening to USI devices.

Bug: 243005009
Test: atest FrameworkServicesTests
Change-Id: I336c4c183d7f44ebdbd93a130fe204ddcad4617c