Unify msggenerator

[DiamondJoseph]

Fixes #ISSUE

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 95.02%. Comparing base (9cb9596) to head (58db200).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #838      +/-   ##
==========================================
- Coverage   95.02%   95.02%   -0.01%     
==========================================
  Files         117      117              
  Lines        4765     4762       -3     
==========================================
- Hits         4528     4525       -3     
  Misses        237      237              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[DiamondJoseph]

Duplicate of #832 🤷