[clang-tidy] bugprone-reserved-identifier will not emit a diagnostic for declarations if the identifier is used in an invoked macro

The bugprone-reserved-identifier check is supposed to identify declarations which use names reserved by the C/C++ standard.

E.g.:

```c++
// declarations for which I would expect diagnostics from bugprone-reserved-identifier
void __foo() {}
int __x{};
```

That works for the most part, but if those symbols are used inside an invoked macro, then bugprone-reserved-identifier won't report them at all.
I would understand if it would report them, but not provide a FixIt.

To reproduce ([godbolt](https://godbolt.org/z/3c36G3qxj)):

```c++
void __foo() {}
void __bar() {}

int __x{};
int __y{};

#define FOO __foo
#define BAR __bar
#define X __x

int main() {
__foo();
BAR();

return X;
}
```

```bash
clang-tidy --checks="-*,bugprone-reserved-identifier" test.cpp
```

For `__foo` and `__y`, diagnostics are emitted, but not for `__bar` and `__x`.

Start with the bugprone-reserved-identifier check and reproduce the issue using the provided test.cpp example and clang-tidy command. Trace why declarations referenced through invoked macros are skipped; done means diagnostics are emitted for __bar and __x as well as the directly used reserved identifiers, with any existing FixIt behavior preserved unless the tests require otherwise.

Written by the indexing model from the issue text.