[clang] [clang] Add `intrin0.h` header to mimic `intrin0.h` used by MSVC STL for clang-cl (PR #75711)

[Casey Carter via cfe-commits]

https://github.com/CaseyCarter approved this pull request.

Thanks for devising this clever way to improve MSVCSTL throughput!

https://github.com/llvm/llvm-project/pull/75711