[SYCL] Add fsycl-id-queries-fit-in-int support for id class

[wenju-he]

This patch also removes two __SYCL_ASSUME_INT from item class. They
becomes redundant since MIndex is implemented using id.

This patch intends to fix performance regression of vectorization on cpu device due to change in #5385: when sycl::id type is used, it won't be converted to sycl::item.
sycl::item already has fsycl-id-queries-fit-in-int support support since #1685.

[Naghasan]

I don't think this is a valid assumption to add, id and range are user constructible, item, nd_item etc. aren't as they represent one of the underlying id query. I believe that's the reason the assumption wasn't added to id and range.

[wenju-he]

https://github.com/intel/llvm/pull/1685/files#diff-8b1e5b8e647706812389238c2a1adf8d3a3e61c198889ad1c14ffe1564326a68 does add __SYCL_ASSUME_INT to id

[wenju-he]

This PR has unnecessary impact on other classes like accessor which also uses sycl::id, so I think we might need a specialized sycl::id with fsycl-id-queries-fit-in-int support that is used within parallel_for kernel for querying global_id. The implementation might be complicated.
After some investigation, I choose to revert #5385 and close this PR.
Revert PR: #6013