Update cpp custom ops docs with sycl extension and xpu support#3391

ZhaoqiongZ wants to merge 5 commits intopytorch:mainpytorch/tutorials:mainfrom

ZhaoqiongZ:update_xpu_custom_ops_docs/zzqZhaoqiongZ/tutorials:update_xpu_custom_ops_docs/zzqCopy head branch name to clipboard