Remove BatteryStatsService.getStatistics*() methods

The format of the returned stream was a parcel. Since BatteryStatsImpl
has been removed from the Framework, it is no longer possible to
unparcel that stream.

Bug: 237123658
Test: atest FrameworksServicesTests:BatteryStatsTests
NoNonSdkCheck: BatteryStatsImpl has being permanently moved to a different package, making it impossible to maintain the implementations of getStatistics or getStatisticsStream.  Any data returned by these methods is available via `dumpsys batterystats`
Change-Id: I4e547f5ab4a44a379dcc19463345cc815b4085c7