make turbo slit have readable children

[stan-dot]

Fixes #1051

Instructions to reviewer on how to test:

1. Do those steps on the device Test out NEXUS file writing i20-1-bluesky#8 (comment)
2. Confirm correct even documents are sent into the RMQ

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 97.68%. Comparing base (b6270c2) to head (9f2031e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1052   +/-   ##
=======================================
  Coverage   97.68%   97.68%           
=======================================
  Files         160      160           
  Lines        6599     6600    +1     
=======================================
+ Hits         6446     6447    +1     
  Misses        153      153           

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