[webrtc-stats] Some RTCSentRtpStreamStats should be moved to Outbound dictionary (#486)

vr000m has just created a new issue for https://github.com/w3c/webrtc-stats:

== Some RTCSentRtpStreamStats should be moved to Outbound dictionary ==
Base RTCSentRtpStreamStats should only contain measurements that can be sent over RTCP or that can be measured independently because these measurements should show up in remote Outbound `dictionary RTCRemoteOutboundRtpStreamStats : RTCSentRtpStreamStats`, which I dont think is possible for the following metrics.
```
unsigned long      packetsDiscardedOnSend;
unsigned long long bytesDiscardedOnSend;
```

fecPacketsSent might make sense as they can be independently measured by the two endpoint but fecPacketsSent would suggest otherwise.

 cc:@henbos @karthikbr82 comments?



Please view or discuss this issue at https://github.com/w3c/webrtc-stats/issues/486 using your GitHub account