Add shear_heating and div_k_grad blending operators

operators.toml

operators/CMakeLists.txt

operators/curl_curl/N1E1ElementwiseCurlCurl.cpp

operators/diffusion/P1ElementwiseDiffusion.cpp

operators/diffusion/P1ElementwiseDiffusion.hpp

operators/diffusion/P2ElementwiseDiffusion.cpp

operators/diffusion/P2ElementwiseDiffusion.hpp

operators/diffusion/P2ElementwiseDiffusionAnnulusMap.cpp

operators/diffusion/P2ElementwiseDiffusionAnnulusMap.hpp

...s/diffusion/P2ElementwiseDiffusionIcosahedralShellMap.cpp

...s/diffusion/P2ElementwiseDiffusionIcosahedralShellMap.hpp

operators/div_k_grad/CMakeLists.txt

operators/div_k_grad/P1ElementwiseDivKGrad.cpp

operators/div_k_grad/P2ElementwiseDivKGrad.cpp

operators/div_k_grad/P2ElementwiseDivKGradAnnulusMap.cpp

operators/div_k_grad/P2ElementwiseDivKGradAnnulusMap.hpp

...s/div_k_grad/P2ElementwiseDivKGradIcosahedralShellMap.cpp

...s/div_k_grad/P2ElementwiseDivKGradIcosahedralShellMap.hpp

...ad/avx/P2ElementwiseDivKGradAnnulusMap_apply_macro_2D.cpp

...ulusMap_computeInverseDiagonalOperatorValues_macro_2D.cpp