libclc: remove __attribute__((assume)) for clspv targets (#92126)

Instead add a proper attribute in clang, and add convert it to function
metadata to keep the information in the IR. The goal is to remove the
dependency on __attribute__((assume)) that should have not be there in
the first place.

Ref https://github.com/llvm/llvm-project/pull/84934

GitOrigin-RevId: 932ca85680db5e4579306f37e55746097fb8ec7f
1 file changed