[llvm] [LLVM-C][OCaml] Update OCaml bindings to match LLVMMetadataKind in C API (PR #132268)

[David Blaikie via llvm-commits]

dwblaikie wrote:

Could we move DebugInfo.h to use the .def file (I seem to recall another recent review where someone was proposing removing .def usage from a C API header because it made it easier for some tooling to process it - but keeping a single source of truth seems more important?)? That doesn't address the "append only" nature - but I guess put big scary comments about that as best we can.

https://github.com/llvm/llvm-project/pull/132268