more tests, bump opencv_core and opencv_dart to 1.3.0

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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 :warning:

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Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/rainyl/opencv_dart/pull/274/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rainy+liu) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/rainyl/opencv_dart/pull/274/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rainy+liu) | `92.03% <90.00%> (+0.55%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=rainy+liu#carryforward-flags-in-the-pull-request-comment) to find out more.

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