Improve inbound/outbound RTP stats

[LVala]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 36.53846% with 33 lines in your changes missing coverage. Please review.

Project coverage is 86.22%. Comparing base (0eb774c) to head (cfc7392).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #134      +/-   ##
==========================================
- Coverage   87.16%   86.22%   -0.95%     
==========================================
  Files          36       36              
  Lines        1854     1887      +33     
==========================================
+ Hits         1616     1627      +11     
- Misses        238      260      +22     

Files	Coverage Δ
lib/ex_webrtc/rtp_sender.ex	87.71% <63.63%> (-3.95%)	⬇️
lib/ex_webrtc/rtp_receiver.ex	66.66% <36.36%> (-4.35%)	⬇️
lib/ex_webrtc/rtp_transceiver.ex	87.00% <40.00%> (-4.36%)	⬇️
lib/ex_webrtc/peer_connection.ex	81.37% <13.33%> (-0.68%)	⬇️

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[mickel8]

Nitpick: we can make this a bit shortert

Suggested change

	retransmitted_packets_sent: non_neg_integer(),
	retransmitted_bytes_sent: non_neg_integer(),
	rtx_packets_sent: non_neg_integer(),
	rtx_bytes_sent: non_neg_integer(),

[LVala]

This is a stat from W3C, so I'd probably leave it as it is for the sake of compatibility. If it was for me to decide, I'd also use rtx_ prefix.