Expose methods for controling the mute state

[stefanceriu]

Your use case

What would you like to do?

Programatically mute or unmute the microphone.

Why would you like to do it?

So that we can sync the mute state between EC and CallKit

How would you like to achieve it?

Expose 2 new javaScript methods that the embedding client can call to 1) mute/unmute the call 2) read the current mute state

Have you considered any alternatives?

Tried finding the button based on one of it's properties and clicking it but that's fragile. Also, reading the mute state from the media device's audio track doesn't really work, presumably the track itself isn't muted.

Additional context

Useful for implementing element-hq/element-x-ios#3050

[toger5]

I will try to work on this. (Starting my day with doing reviews however)

[toger5]

This happened in #2482