OPP: Only start the service from AdapterService

BluetoothOppProvider:
 - Update comments and log messages.
 - Remove startService calls; AdapterService starts OPP.
 - Remove unnecessary braces from switch statements.

BluetoothOppService:
 - Remove unused variables.
 - Rename mBatchs -> mBatches.
 - Add an empty Binder for symmetry with other profiles.

BluetoothOppTransfer:
 - Remove unused PowerManager parameters.

Bug: 67460963
Test: File transfer
Change-Id: Ied9a640b96d59e6c2e6b171b0ac3c08173f0ecd7