Pull Request Readiness Checklist

• Move LayerNorm's implementation from dnn: add layer normalization for vision transformers #23047 to MVN
• Extend MVN to work with element-wise scale/bias

As the results:

• MVN speedup by better implementation by @fengyuentau (TODO: provide perf data)
• Enable LayerNorm on CUDA, OpenVINO, OpenCL (see Doesnt use cuda for specific layer #24064 (comment))

TODO:

• Fix CUDA
• Check fast_forward_ocl
• Test LayerNorm + BatchNorm (input scales + fused scales)

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under Apache 2 License.
• 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