Merge pull request #25792 from asmorkalov:as/HAL_fast_GaussianBlur

Added flag to GaussianBlur for faster but not bit-exact implementation #25792

Rationale:
Current implementation of GaussianBlur is almost always bit-exact. It helps to get predictable results according platforms, but prohibits most of approximations and optimization tricks.

The patch converts `borderType` parameter to more generic `flags` and introduces `GAUSS_ALLOW_APPROXIMATIONS` flag to allow not bit-exact implementation. With the flag IPP and generic HAL implementation are called first. The flag naming and location is a subject for discussion.

Replaces https://github.com/opencv/opencv/pull/22073
Possibly related issue: https://github.com/opencv/opencv/issues/24135

### 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.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/imgproc/include/opencv2/imgproc.hpp

@@ -1536,12 +1536,14 @@ respectively (see #getGaussianKernel for details); to fully control the result r
 possible future modifications of all this semantics, it is recommended to specify all of ksize,
 sigmaX, and sigmaY.
 @param borderType pixel extrapolation method, see #BorderTypes. #BORDER_WRAP is not supported.
+@param hint Implementation modfication flags. See #AlgorithmHint
 
 @sa  sepFilter2D, filter2D, blur, boxFilter, bilateralFilter, medianBlur
  */
 CV_EXPORTS_W void GaussianBlur( InputArray src, OutputArray dst, Size ksize,
                                 double sigmaX, double sigmaY = 0,
-                                int borderType = BORDER_DEFAULT );
+                                int borderType = BORDER_DEFAULT,
+                                AlgorithmHint hint = cv::ALGO_DEFAULT );
 
 /** @brief Applies the bilateral filter to an image.