[Core] Fix ResourceLoader.load cache with relative paths

[AThousandShips]

Paths were not simplified meaning that res://foo.bar was treated differently from ./foo.bar and similar

This matches how paths with the res:// prefix are handled, which are simplified as part of the localize_path

The documentation for load states that these paths are not loaded, that's something to discuss and evaluate in a separate PR though, as this is is specific to ResourceLoader.load and just happens to affect this part as well, and loading relative paths in the resource loader is supported (no claim in the documentation to the contrary)

There are also some potential issues with how threaded loading handles paths that I will look into separately, as it might be more consequential, as opposed to this which is a straightforward fix

• See: Inconsistent treatment of load() from relative path #90029 (doesn't "fix" it as such, the documentation part needs to be discussed further)

[ajreckof]

I see how this can fix the issue but I'm wondering if it won't have problems in more niche cases. In particular I'm wondering wether should not append the "res://" in case it is relative before anything else and handle it exactly the same so that there is exaclty no difference between "res://SomeScript.gd" and "./SomeScript". Maybe there is an actual downside of doing it like that that I didn't see.

For clarification this is what I mens by apennding "res://" first : https://github.com/godotengine/godot/compare/master...ajreckof:Fix-ResourceLoader.load-cache-with-relative-paths?expand=1

[AThousandShips]

This is the least disruptive solution, all it affects is the caching, your suggestion wouldn't change anything, see how the method works:

godot/core/config/project_settings.cpp

Lines 151 to 156 in 29b3d9e

	String ProjectSettings::localize_path(const String &p_path) const {
	String path = p_path.simplify_path();
	if (resource_path.is_empty() || (path.is_absolute_path() && !path.begins_with(resource_path))) {
	return path;
	}

The UID won't fetch anything as it won't be a UID

[akien-mga]

Thanks!

[AThousandShips]

Thank you!

[akien-mga]

Cherry-picked for 4.2.2.