Adds LE Scan Downgrade API for concurrent operations

- Avoids maximum LE scan duty cycle during the concurrent operations
- Adds unit test cases to simulate the concurrent operations

Tag: #feature
Bug: 237351651
Test: atest BluetoothInstrumentationTests:ScanManagerTest
Test: manual test for BT connection with scanning
Change-Id: I34ef6faf83c59ecee547cfc0ceef71571b077c3c