SYCL-Graph currently doesn't support using SYCL reductions in graph nodes, as documented https://github.com/intel/llvm/blob/sycl/sycl/doc/extensions/experimental/sycl_ext_oneapi_graph.asciidoc#11-non-implemented-features-and-known-issues

This issue is to track providing support for that and add tests. If fundamental techical blockers are found, then the spec should be updated to say explicitly this isn't supported.