Simulate a motorRecord

[DominicOram]

It would be useful to be able to use an EpicsAdapter to simulate a motorRecord. Currently we cannot do this as https://github.com/dls-controls/pythonSoftIOC does not support motor records

[DominicOram]

I thought we might be able to get away with using analog records but we can't so this does require some thought. @thomascobb I know that from discussion with @callumforrester DLS is moving away from using the motor record but I think we will need some kind of interim solution for this anyway as it's so pervasive currently.

[coretl]

I suggest the best way is to use the real pmac IOC, and make a simulated GeoBrick. We have a simulator already here: https://github.com/dls-controls/pmac/blob/dls-master/sim/SimPMAC.py which we have been meaning to convert to tickit. The threaded bits can go away and be replaced with the tickit socket interface and on_event handling, but the logic looks about right as it is.

[coretl]

This is a python representation of what the trajectory scan program currently does:
https://github.com/dls-controls/pmac/blob/dls-master/sim/SimPMAC.py#L215
We would want to write a similar routine for the grid scan program and trigger that when the grid scan motion program is run

[DominicOram]

Closing in favor of DiamondLightSource/tickit-devices#2