Contributing a SYCL version

[mgrabban]

Thank you for this nice repo! We at Intel use it as one of our GPU benchmark workloads. We now would like to contribute this SYCL version here.

These are the changes that were made: We took the CUDA version of SimpleGPUHashTable and converted it to SYCL using Intel's DPC++ Compatiblity Tool (DPCT) available here. After that, we made some changes (e.g. added timing code and some optimizations) to use it as a benchmark workload. The SYCL code runs on Intel GPUs, CPUs, NVIDIA GPUs and AMD GPUs. The README has detailed instructions for building and running on these machines.

Any feedback is welcome.