Merge pull request #25382 from savuor:rv/fix_mesh_load

Fix mesh loading for texture coordinates and face indices #25382

### This PR changes

* Texture coordinates were stored incorrectly (3-channel array is read as if there were 2 channels), fixed
* Faces were pushed back to the output array instead of indexed writing which produced a lot of empty faces, fixed
* A set of ground truth tests were added to cover these issues
* `std::vector<cv::Mat>` support added for `saveMesh()` which is required for Python bindings
* More command line args were added to rasterization test data generator

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/3d/misc/python/test/test_iomesh.py

@@ -32,7 +32,7 @@ class raster_test(NewOpenCVTests):
             if a.shape not in goodShapes:
                 self.fail(errorMsg % s)
 
-        if texCoords.shape not in [(1, 18, 2), (18, 1, 2)]:
+        if texCoords.shape not in [(1, 18, 2), (18, 1, 2), (18, 2)]:
             self.fail('texture coordinates array should be 1x18x2 or 18x1x2')
         if isinstance(indices, numpy.ndarray):
             if indices.shape not in [(1, 6, 3), (6, 1, 3)]: