Add Picture-by-Picture (PBP) mode to Power Display

### Description of the new feature / enhancement

The ability to control Picture-by-Picture (PBP) mode from Power Display:
- On/Off
- Aspect ratio
- Screen 1
- Screen 2
- Audio source

### Scenario when this would be used?

I use two computers at the same time every day for work, with the help of Mouse Without Borders and my monitor’s PBP feature. Being able to enable and disable PBP from Power Display to quickly switch between work mode and personal mode without having to get up to press the button on the back of the screen and navigate its ugly interface would be awesome

### Supporting information

_No response_

The issue names Power Display but provides no files, tests, or implementation entry point. First identify how Power Display communicates with monitors and how PBP settings are exposed; done means the five requested controls—on/off, aspect ratio, Screen 1, Screen 2, and audio source—are available there.

Written by the indexing model from the issue text.