Write AIT command to check basic SAM, cable, and ASIC liveness.

The SAM is installed into a cryostat feedthrough box. That needs to be done very early on, after which the DAQ chain gets split up. We need to bundle the basic SAM+ASIC sanity tests (voltages ok? images sane? Number of channels right? etc.) into a single command which can be run on the test bench, with the custom cable, the ASIC, and the ROIC.

We have all the low-level commands to query things: we just need to put those into an actor command (or a few).