Add TCP+Relay detection event

[david-macpherson]

Relevant components:

• Signalling server
• Frontend library
• Frontend UI library
• Matchmaker
• Platform scripts
• SFU

Problem statement:

There is currently no event emitted if the local candidate is relayed over TCP
this can happen if the local candidate is connected to a TURN server and the transport is TCP
This will degrade the stream quality severely

Solution

• Log to the console a Stream quality severely degraded, local connection is relayed over TCP due to the local network environment. message
• Once the stream has started if the local candidate type is relay and the relay protocol is TCP then emit a stream warning event for a user to consume to set their own message

Documentation

To subscribe to the event

	stream.addEventListener('webRtcTCPRelayDetected', (event: WebRtcTCPReldayDectectedEvent) => {
		console.log("TCP + TURN detected: " + JSON.stringify(event.data))
	});
	

[lukehb]

I have left some comments for changes around the specificity of the event, binding to it, and the general detection of the tcp/relay connection.

[lukehb]

Requested some changes around how the stats are intercepted so that it works on each new connection, not just the first one.

[lukehb]

Additionally, it appears the unit tests are now failing against your PR, please look into that too.

[lukehb]

Minor change requested refactoring lambda into a named function

[lukehb]

Request for ambiguous this context change.

[lukehb]

I forgot about the remove listener case, you should revert it to using bind() as the arrow function syntax won't work for the remove case.

[lukehb]

lgtm!