OMS58 and MAXv miscellaneous fixes, enhancements, and changes

[klauer]

The SLAC accelerator side has over the years made a considerable number of changes to the OMS58 and MAXv motor record support.

I made an attempt to separate the two from our motor record fork a couple years ago, but regrettably did not find the time to follow up with the collaboration.

In case it may be of interest to any other facilities, I'd like to link to those branches here.

The MAXv code is here:
https://github.com/klauer/motor/commits/oms_slac_R6-8-RC1_1-13

and OMS58, from SLAC/SPEAR, is here:
https://github.com/klauer/motor/commits/oms58_fixes

Disclaimer: I can't guarantee these work and do not have access to the hardware any longer. As with the other issues I've been creating, feel free to close this if you feel it doesn't belong here.