GDScript: Adjust STATIC_CALLED_ON_INSTANCE warning to not default to the native type, and to not trigger on self-calls

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)

0 files changed, 0 insertions, 0 deletions