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

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

LGTM, thanks for the improvements :)

In the follow-up commits let's pay attention to the `ArrayBound` lower bound check where the code says that _"A symbolic region in unknown space represents an unknown pointer that may point into the middle of an array, so we don't look for underflows."_ and assumes that e.g. a symbolic region in a known space necessarily points to the beginning of a memory area (i.e. negative indices are erroneous).

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