Converting MX Beamlines to device manager

[adaudon]

Fixes #1765

Instructions to reviewer on how to test:

1. Do thing x
2. Confirm thing y happens

Checks for reviewer

• Would the PR title make sense to a scientist on a set of release notes
• If a new device has been added does it follow the standards
• If changing the API for a pre-existing device, ensure that any beamlines using this device have updated their Bluesky plans accordingly
• Have the connection tests for the relevant beamline(s) been run via dodal connect ${BEAMLINE}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.09%. Comparing base (00af332) to head (783ba6d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1788      +/-   ##
==========================================
- Coverage   99.12%   99.09%   -0.03%     
==========================================
  Files         283      283              
  Lines       10736    10745       +9     
==========================================
+ Hits        10642    10648       +6     
- Misses         94       97       +3     

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[tpoliaw]

I think this should be updated to pass oav in to avoid multiple instances