Support `nullptr` value of argument `ptr_C` for xe_array_epilogue#541

sanchitintel wants to merge 5 commits intointel:mainintel/sycl-tla:mainfrom

sanchitintel:allow_nullptr_c_for_array_epiloguesanchitintel/cutlass:allow_nullptr_c_for_array_epilogueCopy head branch name to clipboard