Add onConferenceSupportedChanged callback, carrier config.

Used to inform listeners when a connection can or cannot be part of a
conference.  Used to inform the conference controller so that it can
recalculate the conferencable connections.

Adding carrier config for carrier requirement.

Bug: 29059073
Change-Id: Iab028fd44d87c8dc2bbbe8bba7ba9ccdc223fe51
5 files changed