Add destination directory to load_resource_pack

[mnn]

Godot version: 3.1.beta3.mono

Currently bool load_resource_pack ( String pack ) loads everything and then dumps it directly in res://. I would like to have an option to specify to what (virtual) directory contents of pck will be loaded. It shouldn't be a breaking change, since the new parameter could be optional.

For example after running this:

ProjectSettings.load_resource_pack("mods/mod1.pck", "mod1")

contents of mod1.pck would be accessible in res://mod1/.

[mnn]

Is this a desired feature, has it potential to be merged - should I try implementing it? (Operative word try, since I don't know much about engine internals nor C++.)

If not, I could explore other approaches to my problem, e.g. reading files' paths from pck and rejecting (not loading) invalid mods.

[akien-mga]

Reopening as #35261 was reverted, as it's not so useful without a proper remapping of dependency paths.

[akien-mga]

This should likely be reopened as a more detailed proposal on godot-proposals, with a suggestion on how to handle remapping dependencies to the new path.

See also godotengine/godot-proposals#2689 which is a related proposal (though it doesn't seem to cater to loading in subpaths specifically).