Add developer mode option to show RTC connection statistics

[hughns]

New option in developer settings:

Which overlays some basic info on audio and video when available:

And you can click to get the full RTCInboundRtpStreamStats | RTCOutboundRtpStreamStats data in a modal:

[toger5]

This introduces some odd horizontal scrolling on Firefox:

[toger5]

Could be the tooltip provider?

[hughns]

This introduces some odd horizontal scrolling on Firefox:

Good spot. It's the same on Chrome too.

[hughns]

I've moved the detailed data into a modal and I think it's probably good enough for now.

[toger5]

It is hard to tell how much time and effort we want to put into this.
There are a couple of issues:
your own stream does not show reasonable data:

The styling is hard to read, the buttons are super small.
But I suspect this is just debug information and should not be used by users who want EC to be pretty.
I will give it a quick try to change the css to be a bit more fitting and you can check if you like it.

[toger5]

Here are the proposed changes: #2916