Rewrote plans to use single analyser detector with stronger tests

[oliwenmandiamond]

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 user on a set of release notes

[oliwenmandiamond]

Currently blocked by bluesky/bluesky#1978 and DiamondLightSource/dodal#1803

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (fefb379) to head (17a9225).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #245   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           30        30           
  Lines          774       779    +5     
=========================================
+ Hits           774       779    +5     

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