[llvm] [IR] Allow MDString in operand bundles (PR #110805)

[Nikita Popov via llvm-commits]

nikic wrote:

To check my understanding, the reason why we need the bitcode change is that we only encode the operand type if the value ID is larger than the instruction ID, which is never going to be the case for metadata, so we can't use the type to distinguish metadata? And the reason this is not a problem for normal call arguments is that it doesn't encode the types and instead takes them from the function type?

https://github.com/llvm/llvm-project/pull/110805