[llvm] [AggressiveInstCombine] Fold i64 x i64 -> i128 multiply-by-parts (PR #156879)

[Cullen Rhodes via llvm-commits]

c-rhodes wrote:

#60200 is related, but this is the other pattern I'm aware of that I mention in the summary. I discovered this issue after I started working on this.

https://github.com/llvm/llvm-project/pull/156879