Optimize and clean up ScanController

- Improve encapsulation
- Use `Bytes.reverse` instead of local implementation
- Use `BluetoothUtils.extractBytes` instead of local implementation
- Remove unused import
- Remove "NonApiType" violations

Bug: 394958283
Test: atest ScanControllerTest
Test: atest BassClientStateMachineTest
Flag: Exempt refactor no-op
Change-Id: Ie94eef443e68df7d4303686aed533de1f895e9f7