Invalid FIX-IT performance-single-char performance-prefer-single-char-overloads

Assuming the following code

```c++
#include

#define TOKEN_SEPARATING_CHARACTER "_"

void foo()
{
std::string a;
a += TOKEN_SEPARATING_CHARACTER;
}
```

`performance-single-char-overloads` will apply the following changes.

```c++
#include

#define TOKEN_SEPARATING_CHARACTER "_"

void foo()
{
std::string a;
a += '_';
}
```

This is probably not the expected behavior, we should probably not emit any warning if the string is coming from a define (with an option) rather than removing the define.

https://godbolt.org/z/ccqaajchW

Start by reproducing the issue with the C++ snippet and the performance-single-char-overloads check, then inspect the check's handling of macro-defined strings. Confirm the intended behavior for TOKEN_SEPARATING_CHARACTER and verify that the diagnostic and suggested change no longer produce the invalid replacement shown in the report.

Written by the indexing model from the issue text.