This removes the mostly obsolete 'numIn/Out' range restrictions on nodes.
It also makes it possible to connect optional crossbars that disappear.
val x = TLXbar()
x := master
slave := x
val y = TLXbar()
x :=* y // only connect y if it gets used
This will create crossbar x, but crossbar y will disappear.
When switching ports, the bypass stalls new messages until all
outstanding messages have received their responses. However, this
stall must NOT stop the remaining beats of a partially sent request.
