more tests, bump opencv_core and opencv_dart to 1.3.0

[rainyl]

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[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 92.03%. Comparing base (2815e17) to head (d31129b).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/dartcv/lib/src/core/mat.dart	90.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #274      +/-   ##
==========================================
+ Coverage   91.48%   92.03%   +0.55%     
==========================================
  Files          49       49              
  Lines        9125     9129       +4     
==========================================
+ Hits         8348     8402      +54     
+ Misses        777      727      -50     

Flag	Coverage Δ
unittests	92.03% <90.00%> (+0.55%)	⬆️

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