Pipe statistics (packet loss, lagginess, etc.) from webrtc to the viewer statistics panel.

[roxanneskelly]

We need to display connection health statistics for voice.
The webrtc library has some calls to get these statistics.

Test plan

• Check for the presence of the the following stats in the bottom of the Statistic floater (ctrl+shift+1)

• Verify the values are "n/a" on a Vivox region if you logged in there.
• If you teleport from a WebRTC region to a Vivox region, verify the stats have numbers, but they do not update.
• Verify the values are numeric on a WebRTC region, and they update when you transmit and receive voice.

Is there anything else to verify?

[maxim-productengine]

The following stats are added:

[Dan-Linden]

I saw a very high number of packets lost after teleporting between some vivox and WebRTC regions on Mac.

SecondLife.log

[maxim-productengine]

I tried to teleport between London city region (quite active voice chat) and other vivox regions but wasn't able to repro that issue.
Anyway, I think I know why it's happened - turns out webrtc may report negative packetsLost and we're using unsigned for that.