[clang] Prioritze decl comments from macro expansion site (#65481)

For declarations declared inside a macro, e.g.:
```
`#define MAKE_FUNC(suffix) \
         /// Not selected doc comment \
         void func_##suffix(void) {  }

/// Doc comment foo
MAKE_FUNC(foo)

/// Doc comment bar
MAKE_FUNC(bar)
````

Prefer the doc comment at the expansion site instead of the one defined
in the macro.

rdar://113995729