Not defaulting to the native type rationale:
Defaulting to the native type is less than useful, as:
* There are very few native types that are extensible and have static methods.
* Defaulting to the native type does not account for a method being script-defined.
While the "real fix" would be to carefully track the source of the method, the get_function_signature method is already complicated enough.
This will at least ensure the resulting code should always be valid.
Not triggering on self-calls rationale:
Found in PR comment https://github.com/godotengine/godot/pull/85918#issuecomment-1935864459
```
static func example():
pass
func example2():
example() # self-call on static function
```
Disabling this warning on self-calls is:
* Consistent with other languages
* Important for anonymous classes (where the output code is unusable)
