cryomech: Move PTC class to drivers module

[BrianJKoopman]

Description

This is just a cherry-pick of 32bf784 from #767 that moves the "driver" code out of the cryomech agent module into its own driver module.

Motivation and Context

I want to squash #767, but didn't like how noisy this will make that commit so I wanted to separate it.

How Has This Been Tested?

Not tested separately from #767, but it's a simple move, and #767 will be merged shortly after this is.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.