Add a clause 6.5.7 for Total conversation

The specific for total conversation is that it must fulfil the media quality requirements. New proposal for 6.5.7:

6.5.7 Total conversation

Where continuous bidirectional communication support voice, RTT, and video, with voice meeting the performance requirements of clause 6.1, RTT meeting the performance requirements of 6.2.4 for responsiveness and clause 6.2.6 for processing rate, and video meeting clause 6.5.2 for spatial resolution, clause 6.5.3 for frame rate, and voice and video meeting the requirement of clause 6.5.4 for synchronization,

shall be regarded to meet requirements for synchronization of media and may be called total conversation