Simplify netlist edits around routing

[Coloquinte]

Many edits are performed around routing, such as insertion of power rails/ring/routing pads.
Currently these calls are put in several places and duplicated. For example, setupPowerRails is called in two placed, depending on whether the router is in channel routing mode or not.

It would be nice to put all such netlist edits in a clearly delineated step, so it's easier to know where database modifications are performed and why.