BluetoothManagerService: Setup with custom Looper

Passing a Looper allow test to use a TestLooper and to not have any
issue with asynchronous call.
It is also way easier to check tricky behavior and to check re-entrant
messages
Cleaning serverproxy in the same time

Bug: 262605980
Test: atest ServiceBluetoothTests
Change-Id: Iec56b7efc8d5ae82002209c692a0e39e3922f299