Implement dumpsys bluetooth_manager --proto

Add BluetoothManagerServiceDumpProto for protobuf dumpsys of bluetooth
manager service. Primarily used by incident service to capture an
incident report proto.

Command to invoke (any of the following after lunch and env setup):
$ adb shell dumpsys bluetooth_manager --proto
$ adb shell incident 3050
$ incident_report 3050

Bug: 146085372
Test: Execute the above commands and compare the output against normal
dumpsys

Change-Id: I7ccef334ffeae02316db3afff929998b544972b1