Add logging tip when pin is found and tidy up move to find pin

[DominicOram]

See #924 (not yet fixed but should help to debug)

To test:

1. Confirm that the tip location will be logged whenever one is found
2. Confirm that the changes done (as suggested in #906 check limits during pin tip centring #907 (review)) are more readable and pass the tests still

[codecov]

Codecov Report

Merging #926 (f04a07d) into main (9efd61e) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #926      +/-   ##
==========================================
- Coverage   93.04%   93.03%   -0.01%     
==========================================
  Files          51       51              
  Lines        2459     2456       -3     
==========================================
- Hits         2288     2285       -3     
  Misses        171      171              

Files	Coverage Δ
...hyperion/experiment_plans/pin_tip_centring_plan.py	96.96% <100.00%> (-0.14%)	⬇️

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[noemifrisina]

Looks good to me, logging message shows up and tests pass.