In quicsession, unify num_*_incoming_streams_ and num_*_outgoing_streams_. refactoring only, not protected. Also remove unused GetNumDrainingStreams, GetNumOpenDynamicStreams and GetNumDrainingOutgoingStreams. PiperOrigin-RevId: 314332362 Change-Id: Iccbc9cdf1bc7c2c5101de7de31d68a218e7d0901