Merge #6421

Merge #6421

6421: Check for allow(..) attributes in case check diagnostic r=popzxc a=popzxc

Resolves #6348

This is not a full-fledged solution, as it doesn't looks up for parent elements (e.g. function -> module -> parent module -> crate root), but it does at least checks attributes of item being checked.
I played a bit with code, and it seems that implementing a proper solution (which will also check for `deny` / `warn` attributes overriding values for `allow`s from above).

So, this solution should fix all the macros which intentionally do "weird" naming and wrap it with `allow`, such as `lazy_static`.

cc @ArifRoktim

Co-authored-by: Igor Aleksanov <popzxc@yandex.ru>