Merge pull request #24231 from fengyuentau:halide_cleanup_5.x

dnn: cleanup of halide backend for 5.x #24231

Merge with https://github.com/opencv/opencv_extra/pull/1092.

### 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/src/net_impl.cpp

@@ -104,9 +104,6 @@ void Net::Impl::validateBackendAndTarget()
               preferableTarget == DNN_TARGET_CPU_FP16 ||
               preferableTarget == DNN_TARGET_OPENCL ||
               preferableTarget == DNN_TARGET_OPENCL_FP16);
-    CV_Assert(preferableBackend != DNN_BACKEND_HALIDE ||
-              preferableTarget == DNN_TARGET_CPU ||
-              preferableTarget == DNN_TARGET_OPENCL);
 #ifdef HAVE_WEBNN
     if (preferableBackend == DNN_BACKEND_WEBNN)
     {
@@ -204,16 +201,6 @@ void Net::Impl::setUpNet(const std::vector<LayerPin>& blobsToKeep_)
 
         initBackend(blobsToKeep_);
 
-        if (!netWasAllocated)
-        {
-#ifdef HAVE_HALIDE
-            if (preferableBackend == DNN_BACKEND_HALIDE)
-                compileHalide();
-#else
-            CV_Assert(preferableBackend != DNN_BACKEND_HALIDE);
-#endif
-        }
-
         netWasAllocated = true;
 
         if (dumpLevel)
@@ -808,10 +795,6 @@ void Net::Impl::forwardLayer(LayerData& ld)
                 }
 #endif
             }
-            else if (preferableBackend == DNN_BACKEND_HALIDE)
-            {
-                forwardHalide(ld.outputBlobsWrappers, node);
-            }
             else if (preferableBackend == DNN_BACKEND_INFERENCE_ENGINE_NGRAPH)
             {
                 CV_Assert(preferableBackend != DNN_BACKEND_INFERENCE_ENGINE_NGRAPH && "Inheritance internal error");
@@ -1566,7 +1549,6 @@ string Net::Impl::dump(bool forceAllocation) const
     switch (prefBackend)
     {
     case DNN_BACKEND_DEFAULT: backend = "DEFAULT/"; break;
-    case DNN_BACKEND_HALIDE: backend = "HALIDE/"; break;
     case DNN_BACKEND_INFERENCE_ENGINE:  // fallthru
     case DNN_BACKEND_INFERENCE_ENGINE_NN_BUILDER_2019:  // fallthru
     case DNN_BACKEND_INFERENCE_ENGINE_NGRAPH: backend = "OpenVINO/"; break;