Allow moving aperture and scatterguard more independently

[DominicOram]

Fixes DiamondLightSource/mx-bluesky#267

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 94.47%. Comparing base (b39f55c) to head (be39aac).
Report is 76 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #758      +/-   ##
==========================================
+ Coverage   94.44%   94.47%   +0.02%     
==========================================
  Files         114      114              
  Lines        4588     4612      +24     
==========================================
+ Hits         4333     4357      +24     
  Misses        255      255              

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