Make the default ion pump distribution across controllers BRN/BRN

Each cryostat's ion pumps are currently assigned to the two 4UHV controllers in arm order, with BB and RR on one controller, and NN on the second.

In order to be more resilient in the face of controller failures, change that to put all the first BRN pumps on one controller and the second BRN on the other.

This change will require physically connecting and starting up the controllers to match. Note that there is no way to tell whether the pump which an xcuActor connects to is the right one for that cryostat.