[clang] [clang][StaticAnalyzer] Reduce MallocSizeofChecker false positives for layout-compatible types (PR #200253)

[Balázs Benics via cfe-commits]

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

Still looks good. You could merge it if you want, or we can discuss if we want to further improve it.
I had a couple of actionable improvement opportunities, but I'll leave it up to you if you want to take them or not.

https://github.com/llvm/llvm-project/pull/200253