create lists of latches in each FU, to record the read/write register

create lists of latches in each FU, to record the read/write register
numbers required by the FU to read/write to regfiles.

previously, in the FSM-only version, these read/write regnums were
held (globally) by TestIssuer, and because only one instruction was
active, it did not matter.

now with the possibility of multiple instructions being run, it matters
(a lot)