Not in sync with Elgato Wave:3

## What Happened

When muting the sound input by middle clicking on the indicator or the switch in the dropdown the [Elgato Wave:3](https://www.elgato.com/en/wave-3) updates it's button to red (indicating mute). When I however mute on the Wave nothing in the indicator seems to update.

Same goes when adjusting the input volume / gain. When adjusting the input volume in the indicator leds on the Wave update, while when the input volume is adjusted on the Wave the indicator doesn't update.

This is normally not that big of an issue, but it seems like sometimes the OS overrides the Wave back to the old input volume.
Or in some rare cases it does mute the OS because the Wave is muted, but the the OS doesn't unmute when I unmute on the Wave, meaning I need to also manually unmute the OS.

(Same goes for the audio settings btw)

## Expected Behavior

Ideally the OS (inc the indicator) also updates when mute or input volume / gain is adjusted on the Elgato Wave:3, keeping things in sync both ways.

## Steps to Reproduce

1. Adjust mute or input volume / gain on Wave

## Platform Information

elementary OS 5.1.7 Hera

Start by reproducing the Elgato Wave:3 mute and input-volume changes in the panel-sound indicator and audio settings on elementary OS 5.1.7 Hera. Read the sound indicator's PulseAudio integration and determine how external hardware changes are observed. Done means hardware and OS changes remain synchronized in both directions for mute and input volume.

Written by the indexing model from the issue text.