[llvm] [BPI] Transfer value-handles when assign/move constructing BPI (PR #77774)

[Jeremy Morse via llvm-commits]

jmorse wrote:

Thanks for the review; I'll merge shortly and file a cherry-pick request to the llvm-18 release branch, as I imagine most people want less nondeterminism in their compilers.

https://github.com/llvm/llvm-project/pull/77774