Separate category controller out of HearingDeviceControlsController

We're going to add more different device controls (such as hearing aids presets, volume offset controls or microphone volume controls) into "device_controls_general" PreferenceCategory. It's better to keep the category controller separated from the child controller to better maintain the visibility of the whole category and have a clearer stucture of these controllers.

Bug: 300015207
Test: atest BluetoothDetailsHearingDeviceControllerTest
Test: atest BluetoothDetailsHearingDeviceSettingsControllerTest
Test: atest BluetoothDeviceDetailsFragmentTest
Change-Id: I7f35b02a1120aefa8307e500f7abfce3b8055fbf