[llvm] [mlir] [ADT] Add implementations for mulhs and mulhu to APInt (PR #84609)

[Shourya Goel via llvm-commits]

Sh0g0-1758 wrote:

@RKSimon, could you drop a confirmation about assertion statements? I think apart from that, this looks good to land. 

https://github.com/llvm/llvm-project/pull/84609