Allow specifying the grid size in microns

[DominicOram]

Fixes #845

To test:

1. Confirm tests still pass

[codecov]

Codecov Report

Merging #846 (b8153c5) into main (4ee4e97) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #846   +/-   ##
=======================================
  Coverage   94.60%   94.60%           
=======================================
  Files          42       42           
  Lines        2112     2114    +2     
=======================================
+ Hits         1998     2000    +2     
  Misses        114      114           

Files Changed	Coverage Δ
src/artemis/experiment_plans/full_grid_scan.py	100.00% <ø> (ø)
...rtemis/experiment_plans/oav_grid_detection_plan.py	100.00% <100.00%> (ø)
...plan_specific/grid_scan_with_edge_detect_params.py	96.00% <100.00%> (+0.08%)	⬆️

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[d-perl]

probably should update params version, otherwise great

[DominicOram]

Sure, I think given it's optional and we just did a v6 release I only want to bump a minor Artemis version though

[DominicOram]

Given parameter change could you review https://gerrit.diamond.ac.uk/c/gda/gda-mx/+/39676 too