Plumb SP Bank Version information to MGS

[andrewjstone]

The control plane/mupdate will need to know which software version is installed on each bank of the SP. We will use this so that we can control boot selection and match versions for redundancy once a version has been deemed "good".

[andrewjstone]

Assigned to @mkeeter as he is working on getting this information from the caboose to MGS this afternoon.

[jgallagher]

I believe this is done as of oxidecomputer/management-gateway-service#91 and oxidecomputer/omicron#3239.