[clang] [clang-tools-extra] [clang-tidy][dataflow] Add `bugprone-null-check-after-dereference` check (PR #84166)

[via cfe-commits]

martinboehme wrote:

Some general comments:

*  Is this ready for the next round of review? I see you've pushed a change, but you remark in other comments that there are still changes left to do. Can you let us know when this is ready for review again?

*  When updating the PR, can you [use fixups instead of force-pushing](https://llvm.org/docs/GitHub.html#updating-pull-requests)? This makes it easier to see what you've changed.

*  This PR has a _lot_ of reviewers on it. I'd suggest keeping the ones who have made comments so far and removing the others. (They can always re-add themselves if they want to, but a PR shouldn't generally need this many reviewers.)

https://github.com/llvm/llvm-project/pull/84166