ENH: add class for mr1l1

[nrwslac]

Description

• add class XOffsetMirrorNoBend for mr1l1

Motivation and Context

• mr1l1 installed on the beamline

How Has This Been Tested?

• launched a typhos screen for MR1L1:HOMS.

Where Has This Been Documented?

https://jira.slac.stanford.edu/browse/ECS-1222

Pre-merge checklist

• Code works interactively
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[ZLLentz]

This implies that we should refactor the mirror classes at some point to have a more straightforward inheritance, but it doesn't have to be now.

The implementation looks normal to me and the docstring is clear.