[llvm] [OpenMP][OMPIRBuilder] Use OMPKinds.def to specify callback metadata (PR #142753)

[Ivan R. Ivanov via llvm-commits]

ivanradanov wrote:

The `VarArgsArePassed` was `true` before, so I left it like that but do these function ever take variadic args? Should that be changed to `false`?

https://github.com/llvm/llvm-project/pull/142753