clang-tidy: modernize-concat-nested-namespaces has false positives and deletes macros with fixits

[Skylion007]

I tried running modernize-concat-nested-namespaces on the entire PyTorch repo and found some edge cases.

Specifically,

namespace a {
namespace b {
}
/* IMPORTANT IFDEF AND MACROS HERE */
}

Where any important ifdef logic or macros are deleted in the fixit (which breaks compilation later), which is definitely not ideal. It would be great if the check didn't apply the fixit where important non-namespace comments, macros, or other code is not deleted.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

[v1nh1shungry]

A revision that should prevent modernize-concat-nested-namespaces from complaining and giving fix-it when there're preprocessor directives like macro definitions between the namespaces: https://reviews.llvm.org/D141787.

[HerrCai0907]

incorrect fix hint has been fixed in https://reviews.llvm.org/D147194