Remove usages of `opencl_constant` attribute from DPC++ library headers

[bader]

The patch adding address space attributes to llvm-project repository doesn't support opencl_constant attribute and using this attribute in DPC++ headers leads to the crash (here).

In particular this attribute is defined in https://github.com/intel/llvm/blob/sycl/sycl/include/CL/sycl/access/access.hpp#L116 and used:

• in internal template function specialization https://github.com/intel/llvm/blob/sycl/sycl/include/CL/sycl/access/access.hpp#L222-L225 (should be quite easy to remove)
• for printf extension https://github.com/intel/llvm/blob/sycl/sycl/include/CL/sycl/ONEAPI/experimental/builtins.hpp#L13-L17 and https://github.com/intel/llvm/blob/sycl/sycl/include/CL/sycl/ONEAPI/experimental/builtins.hpp#L62 (additional work is required to emit valid SPIR-V module).

[bader]

opencl_constant attribute support should be removed from the DPC++ compiler as well.
If it's not removed during https://reviews.llvm.org/D89909 integration to DPC++, we should file another issue on that.