add xobjdetect and ximgproc modules

[rainyl]

• [x] xobjdetect
  • [x] WBDetector
• [ ] ximgproc
  • [x] cv::ximgproc::anisotropicDiffusion
  • [x] cv::ximgproc::edgePreservingFilter
  • [x] cv::ximgproc::findEllipses
  • [x] cv::ximgproc::niBlackThreshold
  • [x] cv::ximgproc::PeiLinNormalization
  • [x] cv::ximgproc::thinning
  • [ ] Structured forests for fast edge detection
  • [ ] EdgeBoxes
  • [ ] Filters
  • [ ] Superpixels
  • [ ] Image segmentation
  • [ ] Fast line detector
  • [ ] EdgeDrawing
  • [ ] Fourier descriptors
  • [ ] Binary morphology on run-length encoded image

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 76.92308% with 6 lines in your changes missing coverage. Please review.

Project coverage is 90.29%. Comparing base (b16eb1b) to head (f430cc0).

Files	Patch %	Lines
lib/src/contrib/ximgproc.dart	76.92%	6 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #72 +/- ## ========================================== - Coverage 90.36% 90.29% -0.07% ========================================== Files 35 36 +1 Lines 5322 5348 +26 ========================================== + Hits 4809 4829 +20 - Misses 513 519 +6 ```

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