This PR follows our previous [RFC ](https://discourse.llvm.org/t/rfc-add-xegpu-dialect-for-intel-gpus/75723) to add XeGPU dialect definition for Intel GPUs. It contains dialect, type, attributes and operators definitions, as well as testcases for semantic checks. The lowering and optimization passes will be issued with separated passes. --------- Co-authored-by: Mehdi Amini <joker.eph@gmail.com>