Change RingtonePickerActivity to extend AppCompatActivity.

The application will continue to display an alert dialog as its main landing screen. We are also adding Hilt to the project to help us with the dependency injection.

Bug: 275540178
Test: com.android.soundpicker.RingtonePickerViewModelTest
Change-Id: Ie6a8fc5c4741d894166ed0c54b39e19d8a6a9161