Merge pull request #27002 from GenshinImpactStarts:magnitude

[HAL RVV] impl magnitude | add perf test #27002

Implement through the existing `cv_hal_magnitude32f` and `cv_hal_magnitude64f` interfaces.

**UPDATE**: UI is enabled. The only difference between UI and HAL now is HAL use a approximate `sqrt`.

Perf test done on MUSE-PI.

```sh
$ opencv_test_core --gtest_filter="*Magnitude*"
$ opencv_perf_core --gtest_filter="*Magnitude*" --perf_min_samples=300 --perf_force_samples=300
```

Test result between enabled UI and HAL:
```
                 Name of Test                     ui    rvv      rvv    
                                                                  vs    
                                                                  ui    
                                                              (x-factor)
Magnitude::MagnitudeFixture::(127x61, 32FC1)    0.029  0.016     1.75   
Magnitude::MagnitudeFixture::(127x61, 64FC1)    0.057  0.036     1.57   
Magnitude::MagnitudeFixture::(640x480, 32FC1)   1.063  0.648     1.64   
Magnitude::MagnitudeFixture::(640x480, 64FC1)   2.261  1.530     1.48   
Magnitude::MagnitudeFixture::(1280x720, 32FC1)  3.261  2.118     1.54   
Magnitude::MagnitudeFixture::(1280x720, 64FC1)  6.802  4.682     1.45   
Magnitude::MagnitudeFixture::(1920x1080, 32FC1) 7.287  4.738     1.54   
Magnitude::MagnitudeFixture::(1920x1080, 64FC1) 15.226 10.334    1.47   
```

Test result before and after enabling UI:
```
                 Name of Test                    orig    pr       pr    
                                                                  vs    
                                                                 orig   
                                                              (x-factor)
Magnitude::MagnitudeFixture::(127x61, 32FC1)    0.032  0.029     1.11   
Magnitude::MagnitudeFixture::(127x61, 64FC1)    0.067  0.057     1.17   
Magnitude::MagnitudeFixture::(640x480, 32FC1)   1.228  1.063     1.16   
Magnitude::MagnitudeFixture::(640x480, 64FC1)   2.786  2.261     1.23   
Magnitude::MagnitudeFixture::(1280x720, 32FC1)  3.762  3.261     1.15   
Magnitude::MagnitudeFixture::(1280x720, 64FC1)  8.549  6.802     1.26   
Magnitude::MagnitudeFixture::(1920x1080, 32FC1) 8.408  7.287     1.15   
Magnitude::MagnitudeFixture::(1920x1080, 64FC1) 18.884 15.226    1.24   
```

### 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
- [ ] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [ ] 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/core/src/mathfuncs_core.simd.hpp

@@ -273,7 +273,7 @@ void magnitude32f(const float* x, const float* y, float* mag, int len)
 
     int i = 0;
 
-#if CV_SIMD
+#if (CV_SIMD || CV_SIMD_SCALABLE)
     const int VECSZ = VTraits<v_float32>::vlanes();
     for( ; i < len; i += VECSZ*2 )
     {
@@ -306,7 +306,7 @@ void magnitude64f(const double* x, const double* y, double* mag, int len)
 
     int i = 0;
 
-#if CV_SIMD_64F
+#if (CV_SIMD_64F || CV_SIMD_SCALABLE_64F)
     const int VECSZ = VTraits<v_float64>::vlanes();
     for( ; i < len; i += VECSZ*2 )
     {