Expose janus/rtp plugin packet-loss count as gauge

[kris-lab]

Depends on https://github.com/cargomedia/janus-gateway-rtpbroadcast/issues/95

[kris-lab]

@njam streams_packet_loss_audio_count or streams_packet_loss_audio_count_total? please review

[njam]

Ah it's actually a "counter" not a "gauge" :)

I don't think we need the -total, because it's a counter already.

[kris-lab]

makes sense and good catch. @njam please re-review

[njam]

lgtm