[listenonly] Rewrite SFU/Kurento listen only bridge

[prlanzarin]

What does this PR do?

This is a mild rewrite of SFU/Kurento's listen only audio bridge. In detail:

• Remove all dependencies the bridge had to the legacy kurento-extension script
  • Rationale: that thing was old. Came from the Flash client. Error prone and hard to read
  • I won't remove that script just yet. It's still used by screen share. I'll do the same to screen share and then remove it from the code base altogether.
• Fix listen only re-connection in Chromium-based browsers >= M78.
• Add a new base class that implements the signalling base to all bbb-webrtc-sfu components;
• Add a new signalling broker class for the listen only SFU bridge (deprecates the listen only related kurento-extension code);
• Add a new stream state service to allow monitoring SFU module's stream state changes from various modules. Transparent to listen only changes, but will be "visible" in subsequent PRs that tackle video/screen sharing re-connection issues;
• Add an util to load streams into and play media elements in SFU-based media modules
  • Rationale: video, screen share and listen only all implement basically that same thing in slightly different ways. I'm centralizing it. I'll re-use that component in screen share/video in subsequent PRs;
• Improve error handling in the SFU listen only bridge
  • Error handling there was basically botched. No proper normalization was present, which ended up generating generic errors all around, making it difficult to discern error causes on log processing and analysis. Full error list in appendix 1.
• Annotate every error log in audio-manager with a bridge identifier (sip|kurento). Helps us separate errors on log analysis.

Closes Issue(s)

None.

Motivation

Outlined above.

More

Appendix 1: SFU listen only bridge errors and logCode to catch them

Errors will be funneled through logCode: "audio_failure" with extraInfo fields of interest errorCode, cause and bridge

  Format is <errorCode>: <cause>

  1xxx: client-side errors
  ===
  1001: "WEBSOCKET_DISCONNECTED",
  1002: "WEBSOCKET_CONNECTION_FAILED",
  1005: "PEER_NEGOTIATION_FAILED",
  1007: "ICE_STATE_FAILED",

  2xxx codes are server-side bbb-webrtc-sfu errors
  ===
  2000: "MEDIA_SERVER_CONNECTION_ERROR",
  2001: "MEDIA_SERVER_OFFLINE",
  2002: "MEDIA_SERVER_NO_RESOURCES",
  2003: "MEDIA_SERVER_REQUEST_TIMEOUT",
  2004: "MEDIA_SERVER_GENERIC_ERROR",
  2020: "ICE_ADD_CANDIDATE_FAILED",
  2021: "ICE_GATHERING_FAILED",
  2022: "ICE_STATE_FAILED",
  2200: "MEDIA_GENERIC_ERROR",
  2201: "MEDIA_NOT_FOUND",
  2202: "MEDIA_INVALID_SDP",
  2203: "MEDIA_NO_AVAILABLE_CODEC",
  2208: "MEDIA_GENERIC_PROCESS_ERROR",
  2209: "MEDIA_ADAPTER_OBJECT_NOT_FOUND",
  2210: "MEDIA_CONNECT_ERROR",
  2211: "MEDIA_NOT_FLOWING",
  2300: "SFU_INVALID_REQUEST",