Enable ssrc-rewriting by default, it can still be overwritten via config.js

* feat(ssrc-rewriting) Advertise support to Jicofo.

* Fix unit test

* Remove support for legacy endpoint based signaling and make source-name signaling as the only signaling mode. The legacy screensharing mode will no longer be supported. The client will still be able to process remote presence sent in the old format to support interop with very old mobile clients and jigasi that do not support source-name signaling.
* remove code related to presenter mode.

Handle presence updates for multiple sources per remote endpoint.

Also switch to using signalingLayer.getPeerSourceInfo during remote track creation when source-name signaling is used.

...to advertise track's muted state and the video type.

For now, if the source name signaling flag is enabled, both legacy and
new <SourceInfo> element will be used at the same time. This is to be
able to interoperate with legacy clients and start testing the new
format at the same time. Whenever possible <SourceInfo> will be used
as main source of truth with the fallback to legacy <audiomuted/>,
<videomuted/> and <videotype/> elements.