[battery] add BatteryTableLog for the repository

Also change the flows (which are already originating from StateFlows) to
be defined as StateFlow so that the logs are less spammy. This should
also help ensure minimal updates in the whole pipeline.

Test: BatterRepositoryTest
Bug: 411990519
Flag: EXEMPT logging
Change-Id: I8ba265fc8dc7efab6b65e1e82a79feabee66949d