[llvm] [CodeGen] Update for scalable MemoryType in MMO (PR #70452)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Do you mean if we changed it internally too? Yeah that would lose the info I think. I'm not sure if it could come from the type of the load/store instead?
> 

It cannot in the case of extending vector load/truncating vector store. The current legalization for load/store is a total mess. I've had a WIP patch rewriting it for about 4 years which I really need to get back to 

https://github.com/llvm/llvm-project/pull/70452