[le audio] BassClient use exported receiver for BluetoothLeBroadcastAssistant intent

Current BassClientService failed to receive the intent from
BluetoothLeBroadcastAssisant. This commit is to fix this receiver to be
exported which also matches the setting in AndroidManifest.xml BassClientServiceTest.java.

Bug: 292644006
Tag: #bug
Test: atest BassClientServiceTest
Test: manual check intent is received

Change-Id: I9c61398d294dc7df107cf2abdf816a3716f8f975