Add Mbs driver and region classes

[oliwenmandiamond]

Fixes #2068. This implements the MbsRegion and MbsAnalyserDriverIO using the base electron analyser classes. This has updated the testing framework to be much more flexible, allowing for sequence files to be loaded directly to given regions to tests and paired with other fixtures (e.g associated detector and driver) without needing the files to have same number and named regions.

Note: I have removed the image and spectrum pv's from base (for now). This is because Mbs does not use the spectrum like Specs and VGScienta does. I also don't think they are needed from speaking with controls and understanding how the HDF file writer plugin works and will be next bit of work to do once this is complete.

Instructions to reviewer on how to test:

1. Check tests pass
2. Check logic makes sense.

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 99.12%. Comparing base (767b87c) to head (c616463).

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #2056    +/-   ##
========================================
  Coverage   99.12%   99.12%            
========================================
  Files         336      340     +4     
  Lines       13065    13198   +133     
========================================
+ Hits        12951    13083   +132     
- Misses        114      115     +1     

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