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/perf/perf_math.cpp

@@ -36,6 +36,27 @@ PERF_TEST_P(VectorLength, phase64f, testing::Values(128, 1000, 128*1024, 512*102
     SANITY_CHECK(angle, 5e-5);
 }
 
+///////////// Magnitude /////////////
+
+typedef Size_MatType MagnitudeFixture;
+
+PERF_TEST_P(MagnitudeFixture, Magnitude,
+    testing::Combine(testing::Values(TYPICAL_MAT_SIZES), testing::Values(CV_32F, CV_64F)))
+{
+    cv::Size size = std::get<0>(GetParam());
+    int type = std::get<1>(GetParam());
+
+    cv::Mat x(size, type);
+    cv::Mat y(size, type);
+    cv::Mat magnitude(size, type);
+
+    declare.in(x, y, WARMUP_RNG).out(magnitude);
+
+    TEST_CYCLE() cv::magnitude(x, y, magnitude);
+
+    SANITY_CHECK_NOTHING();
+}
+
 // generates random vectors, performs Gram-Schmidt orthogonalization on them
 Mat randomOrtho(int rows, int ftype, RNG& rng)
 {