Fixes for IMS Conferences via the RemoteConnectionService API.

IMS Conferences are problematic to Telecom when a connection manager is
used.  Both addExistingConnection and addConference will result in the
addition of duplicate conference participants and conferences to Telecom.
This is because Telecom does not have a means of de-duping the two, which
have new IDs created for them when they're added via a ConnectionService.

To fix this, added a workaround which packages the original existing
connection or conference id into the connection/conference extras which
are sent to the connection manager.  This way, the connection mgr can use
the same connection/conference ID was was used by the original
ConnectionService, and also perform some de-duping.

Its not optimal, and this should be fixed better in the future.

Bug: 31464792
Change-Id: I7b63f145c741c29e1735f50a473585f26ef70fc7