Initial plumbing for metrics. (#2950)

* Initial plumbing for metrics.

This implements
- metrics received from participant.
- callback to room.
- room distributes it to all other participants (excluding the sending
  participant).
- other participants forward to client.
- counting metrics bytes in data channel stats

TODO:
  - recording/processing/batching
  - should recording/processing/batching happen on publisher side or
    subscriber side?
  - should metrics be echoed back to publisher?
  - grants to publish/subscribe metrics.

* mage generate

* clear OnMetrics on close

* - CanSubscribeMetrics permission.
- Echo back to sender.

* update deps

* No destination identities for metrics

* WIP

* use normalized timestamp for server injected timestamps

* compile

* debug log metrics batch

* correct comment

* add baseTime to wire

* protocol dep

* Scope metrics forwarding to only participants that a participant is
subscribed to.

Also remove the participant_metrics.go file as it was not doing anything
useful.

* update comment

* utils.ErrorIsOneOf

* couple of more utils.CloneProto

test/client/client.go

@@ -694,7 +694,6 @@ func (c *RTCClient) PublishData(data []byte, kind livekit.DataPacket_Kind) error
 	}
 
 	dpData, err := proto.Marshal(&livekit.DataPacket{
-		Kind: kind,
 		Value: &livekit.DataPacket_User{
 			User: &livekit.UserPacket{Payload: data},
 		},