Refactored STUN/TURN fetch to be done only once, when successful, per session and cache it in mem to avoid too many reqs. Current way is a bit dumb, this should increase reliability a bit more. The caching is configurable so folks who want to use very short lived TURN credentials can disable it

Add a fallback STUN config option to be used when the default STUN/TURN fetch fails

Clean the safari/no candidate generation pre flight check from 3rd party STUNs

Fix deadlock in audio join when STUN/TURN fetch failed

Also added some client logging for those cases

Moved video-provider gUM fallback detection to be used only on recvonly streams

This used to be a feature in the Flash client and this is necessary for presentation remotes to work with the HTML client.

Also tidy some stray lines

Propagating configs to WebRTC screenshare script and added support for STUN/TURN config to SFU components