Cleanup code before adding Kosmoses

- move touches input functionality to the VolumeDialogSliderViewBinder to reduce the amount of view binders;
- remove useless VolumeDialogResources;
- make handler nullable in the VolumeDialogCallbackInteractor;

Flag: com.android.systemui.volume_redesign
Bug: 369993864
Test: passes presubmits
Test: manual on the phone. Observe the new Volume Dialog
Change-Id: I5d5dbc530546382c3db58e50ce9a45ed92db9b69