Add keyboard and OSD support audio devices with native volume control and mute (for the sake of consistency)

[waydabber]

This would allow a slider for the built-in display or other audio devices as well. Would be useful for multi-output audio devices where external displays and other devices are combined as well.

Original request for MonitorControl: MonitorControl/MonitorControl#1444

Volume keys should control the MacBook's volume when the cursor is on the MBP screen, and the monitor's volume when the cursor is on the monitor's screen. This is handy when using SoundSource to manage audio for different apps.

[chantalgo]

Request also found on discussions: #2194 (comment)

[waydabber]

This is needed to make the new Tahoe custom OSD styles look consistent. It is annoying to have the app OSD shown when the display's volume is controlled but the system OSD when an other device is being controlled.

[waydabber]