[clang] [nfc][analyzer] Add MemSpace trait to program state (PR #123003)

[Gábor Horváth via cfe-commits]

Xazax-hun wrote:

> This expression is indeed error-prone, but the problem is not the use of isa but the use of the method getMemorySpace()

My bad! You are right, it is not the `isa`. :) 

>  this error-prone situation will be resolved soon in a follow-up commit 

I think it would be nice if we never had the error prone APIs to begin with since people can lose interest, or might get hit by a bus and we are left in an unfortunate state. That being said if there is no easy way to make this less error prone I am OK with delaying that to a follow up PR. But might worth exploring if this is something that can be done in a couple hours, why not. 

https://github.com/llvm/llvm-project/pull/123003