[clang] [SSAF][EntityPointerLevel] Add an intermediate data structure DeclPointerLevel (PR #218196)

[Balázs Benics via cfe-commits]

steakhal wrote:

I think the PR summary should be improved before merging because the way its spelled is not self-containing:

> E.g., PointerFlowExtractor can use it to compute the upper bound on pointer levels for an entity. It is needed for fixing the bug reported in rdar://183529483.
>
> First step for:
> rdar://183529483

I know that you tried to address this proactively by leaving a comment with additional context, but that should be really part of the summary - even if it's long. It is fine for it being long.

https://github.com/llvm/llvm-project/pull/218196