Merge pull request #24409 from fengyuentau:norm_kernel

dnn: add shared fastNorm kernel for mvn, instance norm and layer norm #24409

Relates https://github.com/opencv/opencv/pull/24378#issuecomment-1756906570

TODO:

- [x] add fastNorm
- [x] refactor layer norm with fastNorm
- [x] refactor mvn with fastNorm
- [ ] add onnx mvn in importer (in a new PR?)
- [ ] refactor instance norm with fastNorm (in another PR https://github.com/opencv/opencv/pull/24378, need to merge this one first though)

### 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
- [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

modules/dnn/test/test_torch_importer.cpp

@@ -570,10 +570,10 @@ TEST_P(Test_Torch_nets, FastNeuralStyle_accuracy)
         }
         else if (target == DNN_TARGET_CPU_FP16)
         {
-            normAssert(out, refBlob, "", 0.62, 25);
+            normAssert(out, refBlob, "", 0.64, 25);
         }
         else
-            normAssert(out, refBlob, "", 0.5, 1.11);
+            normAssert(out, refBlob, "", 0.5, 1.16);
     }
 }