Make the ophyd pin tip centre device more like the AD one

[DominicOram]

See DiamondLightSource/hyperion#863

Instructions to reviewer on how to test:

1. Confirm tests pass and that the new pin tip detection device is more similar to the old one

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (02d4299) 89.95% compared to head (16962ce) 89.98%.
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #289      +/-   ##
==========================================
+ Coverage   89.95%   89.98%   +0.03%     
==========================================
  Files          82       82              
  Lines        3055     3055              
==========================================
+ Hits         2748     2749       +1     
+ Misses        307      306       -1     

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[dperl-dls]

LGTM