LeAudio: Do not use framework to start/stop scan

This is a continuation of cc32d2d2.
We previously move the register to bypass the framework.
This part will actually start and stop the scanner

Bug: 348562830
Bug: 340740517
Bug: 347880944
Test: Manual: Pair & forget LeAudio device and
      1/ Check that forget is fast (not blocking the UI 2 sec)
      2/ Check in the dumpsys that there is a scanner for Bluetooth
Flag: com.android.bluetooth.flags.leaudio_call_start_scan_directly
Change-Id: Icf6117640c5cf6b002eeed9f683035d84491367c