Merge pull request #25970 from savuor:rv/hal_pyrdown

pyrDown: offset HAL added, IPP removed #25970

Resolves #25976

### Changes
* HAL added for offset support so that border pixels can be fetched from outside of the image ROI (see `BORDER_ISOLATED` parameter)
* IPP removed since there is `pyrUp` instead of `pyrDown` and there's no easy way to fix this other than rewriting it from scratch
* replaced old C call by modern `cv::pyrDown`

### 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
- [ ] 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/imgproc/test/test_filter.cpp

@@ -1192,7 +1192,7 @@ CV_PyramidDownTest::CV_PyramidDownTest() : CV_PyramidBaseTest( true )
 
 void CV_PyramidDownTest::run_func()
 {
-    cvPyrDown( test_array[INPUT][0], test_array[OUTPUT][0], CV_GAUSSIAN_5x5 );
+    cv::pyrDown(test_mat[INPUT][0], test_mat[OUTPUT][0]);
 }