[llvm] [ConstantFolding] Support ptrtoaddr in cast folds (PR #162480)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson approved this pull request.

Thanks for continuing on the ptrtoaddr effort! I plan to get back to this as well soon, updating further passes. I wonder if it makes sense to have a tracking bug with known missing passes to avoid duplicate efforts? 

https://github.com/llvm/llvm-project/pull/162480