Use MifImage class instead of mrconvert

[tsalo]

Keeping as a draft for now.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 77.11864% with 81 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.17%. Comparing base (50e1c2e) to head (1febcfa).

Files with missing lines	Patch %	Lines
src/modelarrayio/utils/fixels.py	77.67%	40 Missing and 35 partials ⚠️
src/modelarrayio/cli/h5_to_mif.py	62.50%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #43      +/-   ##
==========================================
+ Coverage   61.19%   70.17%   +8.97%     
==========================================
  Files          16       16              
  Lines         951     1254     +303     
  Branches      137      214      +77     
==========================================
+ Hits          582      880     +298     
+ Misses        332      301      -31     
- Partials       37       73      +36     

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