Be compatible with SYCL 2020 and SYCL1.2.1 for sycl.hpp (#83259)
- In SYCL2020, SYCL provides one standard header file: <sycl/sycl.hpp>, which needs to be included in every translation unit that uses the SYCL programming API.
- For compatibility with SYCL 1.2.1, SYCL provides another standard header file: <CL/sycl.hpp>, which can be included in place of <sycl/sycl.hpp>.
- SYCL documents this change in [doc](https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#sec:headers-and-namespaces)(4.3).
- SYCL_LANGUAGE_VERSION substitutes an integer reflecting the version number and revision of the SYCL language being supported by the implementation in SYCL 2020. In SYCL1.2.1, the macro name is CL_SYCL_LANGUAGE_VERSION. So these two macros can be used to distinguish SYCL1.2.1 and SYCL2020.
- SYCL 2020 doc: https://registry.khronos.org/SYCL/specs/sycl-2020/pdf/sycl-2020.pdf
- SYCL 1.2.1 doc: https://registry.khronos.org/SYCL/specs/sycl-1.2.1.pdf
Pull Request resolved: https://github.com/pytorch/pytorch/pull/83259
Approved by: https://github.com/malfet
