Exit Bluetooth upon system server request

This will remove some race condition around Bluetooth being re-attached while it is not yet off. Making the system server wait for the process to go down entirely

Bug: 339304157
Bug: 335521878
Bug: 339548431
Test: atest pts-bot,avatar from presubmit (they restart bluetooth a lot)
Flag: com.android.bluetooth.flags.explicit_kill_from_system_server
Change-Id: Id1207c4e362e5f7adc3c6633c68cc539cc757845