FS-10416: [mod_commands] add new outbound channels to an in-progress originate

FS-10416: [mod_commands] add new outbound channels to an in-progress originate

This allows new endpoints (outbound channels) to be called, after an originate
is already in progress, where any of the originally called endpoints need to
continue to ring.

One use case would be to convert a 302 Moved Temporarily destination to SIP
endpoint(s) and then to add the new endpoints to an in-progress originate,
without cancelling any of the other (already ringing) outbound channels.