Bluetooth: Move Bluetooth battery stats tracking (1/2)

Move Bluetooth battery stats tracking to AppScanStats for a more
unified tracking system.

Bug: 37720787
Test: cts-tradefed run cts-dev -m CtsIncidentHostTestCases -t com.android.server.cts.BatteryStatsValidationTest#testBleScans
      Perform BLE scan and check battery stats
Change-Id: Ie6c682374e6e258c291d3a11eede649c7747ef40