[llvm] [mlir] [ADT] Add signed and unsigned mulh to APInt (PR #84719)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> @RKSimon I don't know why Linux build failed ?

I think it was just a ccache failure - I've merged the patch and will keep an eye on it for failures

https://github.com/llvm/llvm-project/pull/84719