[clang] [clang][analyzer] Improve PointerSubChecker (PR #96501)

[Balázs Kéri via cfe-commits]

balazske wrote:

These results look correct according to the checker, but I am not sure if such results are useful or really invalid:
https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_pointersub1&is-unique=on&diff-type=New&checker-name=alpha.core.PointerSub
In these cases the address difference of an (array) member of a struct and start of the struct is taken. According to the checker rules, taking difference of addresses of any variables or member variables is invalid.

https://github.com/llvm/llvm-project/pull/96501