Added openloop version of M22 exit slit crystal gap which records the…

[NSLentz]

… position of the axis as assumed by the stepper drive. When we hit the lower limit switch on the crystal gap it records the openloop position and then doesn't allow the axis to move more than 40 um smaller in gap. This is because the lower limit switch is positioned 40 um in front of where it should be.

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Pre-merge checklist

• Code works interactively
• Code contains descriptive comments
• Test suite passes locally
• Libraries are set to fixed versions and not Always Newest
• Code committed with pre-commit (alternatively pre-commit run --all-files)