[clang] [analyzer] Allow overriding Unknown memspaces using a ProgramState trait (PR #123003)

[Balazs Benics via cfe-commits]

steakhal wrote:

> Use after scope:
> https://lab.llvm.org/buildbot/#/builders/169/builds/8735
> https://lab.llvm.org/buildbot/#/builders/94/builds/4653/steps/17/logs/stdio
> 

Yeey, could you please revert this for me? @vitalybuka 

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