* feat: add 'disableDesktopSharing' option

* ref(ScreenObtainer): simplify init

add method to send a receiver video constraint message

Treats local/remote relayed addresses differently.

Due to it being ran asyncronously, it's possible a replaceTrack operation is
scheduled while there is a valid PC, but by the time it runs was closed.

Accommodate to this situation by pretending everything is just peachy.

fix(JitsiConf...): stop P2P on JVB121

The P2P session must be stopped with '_stopP2PSession' once accepted.

Remote control

Fix when P2P disabled in config

P2P test mode disables automatic switching to P2P when there are 2
participants in the room.

Old config.js versions don't have the p2p property.

This commit changes the way the average stats are being reported to the
analytics backend. Instead of prefixes for the different scenarios
("p2p_", "jvb121_" and no prefix for multi-party calls) we now have
properties that allow to distinguish which scenario an event pertains
to. The query language of the analytics backend can be used to build
appropriate queries that group by those properties.

Additionally, we now report whether the average stats event concerns a
relayed call (a call that's routed via a TURN server) or not.

Will not accept incoming P2P session if it's disabled in the config.

They are really verbose, and add no real value. In addition, log the channel
type once opened.

* ref: Moves the deployment info variables to config.js

instead of using globals.

* feat: If configured, adds the user's region to presence.

* fix: Guards against accessing undefined properties,

and uses the crossRegion variable from the config.

* style: Fixes formatting.

ref: Use STUN/TURN for the P2P connection.

feat(p2p): refactor p2p configuration options

Until we have a default config template, make sure we default to having P2P
enabled.

Also add a preferH264 option for P2P.

P2P react native (work in progress)

Make it possible to use WebSocket instead of DataChannel

Some browsers may not support data channels (hi there, Edge!) and sometimes it
may not be desirable for other reasons.

* ref(JSPC): simplify SSRC owner in P2P

There's no need for any extra extensions for SSRCs owner signalling in
P2P, because it's always the remote peer who owns them.

This also fixes a problem where no SSRC owner was added for 'source-add'
in P2P (for JVB conference Jicofo adds that).

* fix(TPC): always advertise 'sendrecv'

Our media direction is only ever updated on the remote side with
the initial offer (or answer). Because of that we want to advertise
'sendrecv' even if we start with no video (or audio) track.

It is OK to adjust this direction in the localDescription getter,
because it's adjusted again in the setter to the correct value based on
local tracks, so the SDP transformation chain still works fine.

Will crash the code early in case one of the value is undefined (it will
crash later anyway, but makes it harder to guess).

This code would crash on react-native if 'sdpMid' is not defined at all.
Still works as expected with an empty string though.

P2P analytics round 2

Adds session converted to string to the error object.