Add sycl_ext_oneapi_kernel_compiler_opencl to the supported extensions list

The [sycl_ext_oneapi_kernel_compiler_opencl](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/experimental/sycl_ext_oneapi_kernel_compiler_opencl.asciidoc) is currently experimental extension while actual products such as Pytorch rely on it in the shipped products. Can this extension be promoted from experimental to supported?

See: https://github.com/pytorch/pytorch/blob/v2.13.0/c10/xpu/XPUFunctions.cpp#L179
See: https://github.com/uxlfoundation/oneDNN/blob/v3.13.1/src/gpu/intel/sycl/engine.cpp#L142
CC: @gmlueck, @EikanWang, @guangyey

Start by reading sycl/doc/extensions/experimental/sycl_ext_oneapi_kernel_compiler_opencl.asciidoc and inspect where the supported extensions list is maintained. Compare its status with the PyTorch XPUFunctions.cpp and oneDNN engine.cpp references; done means the extension is listed as supported consistently with those shipped-product uses.

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