DNN: add the Winograd fp16 support (#23654)

* add Winograd FP16 implementation

* fixed dispatching of FP16 code paths in dnn; use dynamic dispatcher only when NEON_FP16 is enabled in the build and the feature is present in the host CPU at runtime

* fixed some warnings

* hopefully fixed winograd on x64 (and maybe other platforms)

---------

Co-authored-by: Vadim Pisarevsky <vadim.pisarevsky@gmail.com>

modules/core/test/ocl/test_image2d.cpp

@@ -83,7 +83,7 @@ TEST(Image2D, turnOffOpenCL)
         }
         else
             std::cout << "CV_8UC1 is not supported for OpenCL images. Test skipped." << std::endl;
-    
+
         // reset state to the previous one
         cv::ocl::setUseOpenCL(useOCL);
     }