Add sycl_ext_oneapi_work_group_scratch_memory to the supported extensions list

The [sycl_ext_oneapi_work_group_scratch_memory](https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/experimental/sycl_ext_oneapi_work_group_scratch_memory.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/intel/torch-xpu-ops/blob/release/2.14/src/comm/SYCLHelpers.h#L288
CC: @gmlueck, @EikanWang, @guangyey

Start with the experimental extension document at sycl/doc/extensions/experimental/sycl_ext_oneapi_work_group_scratch_memory.asciidoc and inspect how the repository records its supported extensions. Use the SYCLHelpers.h reference in torch-xpu-ops as context; done means the extension appears in the supported list rather than only among experimental extensions.

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