[HAL] split8u RVV 1.0 opencv#26884

### Pull Request Readiness Checklist
* Banana Pi BF3 (SpacemiT K1)
* Compiler: Syntacore Clang 18.1.4 (build 2024.12)
```
Geometric mean (ms)

                  Name of Test                   baseline  hal      hal
                                                    ui               vs
                                                                  baseline 
                                                                     ui
                                                                 (x-factor)
split::Size_Depth_Channels::(127x61, 8UC1, 2)     0.012   0.004     3.12   
split::Size_Depth_Channels::(127x61, 8UC1, 3)     0.019   0.006     2.91   
split::Size_Depth_Channels::(127x61, 8UC1, 4)     0.028   0.011     2.64   
split::Size_Depth_Channels::(127x61, 8UC1, 5)     0.067   0.033     2.02   
split::Size_Depth_Channels::(127x61, 8UC1, 6)     0.084   0.040     2.11   
split::Size_Depth_Channels::(127x61, 8UC1, 7)     0.103   0.055     1.88   
split::Size_Depth_Channels::(127x61, 8UC1, 8)     0.113   0.032     3.50   
split::Size_Depth_Channels::(640x480, 8UC1, 2)    0.454   0.179     2.54   
split::Size_Depth_Channels::(640x480, 8UC1, 3)    0.677   0.298     2.27   
split::Size_Depth_Channels::(640x480, 8UC1, 4)    0.901   0.410     2.20   
split::Size_Depth_Channels::(640x480, 8UC1, 5)    3.781   3.010     1.26   
split::Size_Depth_Channels::(640x480, 8UC1, 6)    4.886   4.009     1.22   
split::Size_Depth_Channels::(640x480, 8UC1, 7)    5.777   4.770     1.21   
split::Size_Depth_Channels::(640x480, 8UC1, 8)    4.596   1.330     3.46   
split::Size_Depth_Channels::(1280x720, 8UC1, 2)   1.377   0.709     1.94   
split::Size_Depth_Channels::(1280x720, 8UC1, 3)   2.091   1.034     2.02   
split::Size_Depth_Channels::(1280x720, 8UC1, 4)   2.744   1.573     1.74   
split::Size_Depth_Channels::(1280x720, 8UC1, 5)   9.542   6.284     1.52   
split::Size_Depth_Channels::(1280x720, 8UC1, 6)   11.114  7.850     1.42   
split::Size_Depth_Channels::(1280x720, 8UC1, 7)   14.083  11.879    1.19   
split::Size_Depth_Channels::(1280x720, 8UC1, 8)   13.524  3.865     3.50   
split::Size_Depth_Channels::(1920x1080, 8UC1, 2)  3.108   1.395     2.23   
split::Size_Depth_Channels::(1920x1080, 8UC1, 3)  4.659   2.128     2.19   
split::Size_Depth_Channels::(1920x1080, 8UC1, 4)  6.127   2.818     2.17   
split::Size_Depth_Channels::(1920x1080, 8UC1, 5)  26.733  16.625    1.61   
split::Size_Depth_Channels::(1920x1080, 8UC1, 6)  31.242  22.414    1.39   
split::Size_Depth_Channels::(1920x1080, 8UC1, 7)  35.968  27.658    1.30   
split::Size_Depth_Channels::(1920x1080, 8UC1, 8)  29.997  8.655     3.47
```
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