Use oneAPI's IntelDPCPPConfig.cmake

[oleksandr-pavlyk]

Instead of custom FindIntelSycl.cmake we could use/reuse oneAPI's config module, located in ${ONEAPI_ROOT}/compiler/latest/linux/IntelDPCPP/IntelDPCPPConfig.cmake (on Linux machines).

[oleksandr-pavlyk]

In order to support building dpctl with intel/llvm sycl bundles we need to vendor a copy of IntelDPCPPConfig.cmake and include it in the repo in cmake/ folder of the project.