Add setting to change audio balance

### Feature Description

Right now there is no setting in DMS, to my knowledge, to change the audio balance. You can change this via pavucontrol but it resets every time the volume is changed.
Here is an example from GNOME:

### Use Case

This is a much needed accessibility setting for people with left-right hearing imbalance and also for people with audio equipment that has balance defects.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

_No response_

### Alternatives/Existing Solutions

pavucontrol but it is not sufficient as explained above

No files, tests, or entry points are identified. Start by locating DMS's existing volume or audio-settings entry point and compare its behavior with pavucontrol; done means exposing a left-right balance setting that persists when the volume changes.

Written by the indexing model from the issue text.