[llvm] [IR] Allow type change in ValueAsMetadata::handleRAUW (PR #76969)

[Orlando Cazalet-Hyams via llvm-commits]

OCHyams wrote:

This seems fairly harmless to me, especially as @jmorse points out `Value::replaceAllUsesWith` will still check types are the same through `Value::doRAUW`, though I'm not sure I understand the use-case very well.

Would it be possible for you to add unittest showing this in action? Otherwise SGTM.

https://github.com/llvm/llvm-project/pull/76969