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

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

Thanks for the updates!

I added some inline remarks, but overall I'm satisfied with the state of this PR and I hope that it can be merged soon.

However, I became a bit uncertain about the plans for follow-up changes, because it seems that there are several locations where the difference between "inherently in `<memory space X>`" and "originally in UnknownSpace, but we deduced that it's in `<memory space X>`" is significant. (I'm not entirely certain about this, because e.g. the schematics and applications of "deducing a memory space" are not yet fixed. This might deserve some additional thinking.)

Previously I strongly supported the idea that in the future we should store the `MemSpace` in a single location, as a state trait -- but if the inherent/acquired difference turns out to be relevant, then perhaps we should "stop after this PR" and stabilize this "hybrid representation" of memory spaces.

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