Bluetooth Codec Settings: Assure flag enabled

Assure flag a2dpOffloadCodecExtensibilitySettings is enabled before
calling BluetoothA2dp API.

Bug: 331612641
Tag: #feature
Test: atest SettingsRoboTests:com.android.settings.development.bluetooth.AbstractBluetoothListPreferenceController
Test: atest SettingsRoboTests:com.android.settings.development.bluetooth.BluetoothCodecListPreferenceControllerTest
Change-Id: Iac33a6c95a544230e034807b320c80a727ade307