[llvm] [IR] Add disjoint flag for Or instructions. (PR #72583)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

This mostly LGTM, but I see two questions that haven't been addressed:

* Should a test be added to Bitcode/compatibility (this seems not to have been done consistently in recent times, but the answer is probably still yes)
* Should the setter/getter be moved to PossiblyDisjointInst (the other discussion does suggest that this should probably be done)

https://github.com/llvm/llvm-project/pull/72583