Allow overriding autoload order via override.cfg (to make modding for Godot games better)

[Qubus0]

As mentioned in this issue #71589 in the main repo

Recap:
Overriding autoloads with an override.cfg ignores the order set in the override. Newly defined autoloads are always loaded last.

Why does this matter? I'm trying to (co-)create a mod loader that works with any Godot game. The loader itself is an autoload. Using the override.cfg, we can 'install' it into a game without having to touch or modify its source code. The loader always being last limits the capabilities for extending existing autoloads heavily.

The details of the issue were very well explained by @akien-mga, including an idea

override.cfg does override the values of existing properties, and appends new property/value pairs which aren't present in the original project.godot.

The problem here is that autoloads as registered as properties themselves. And there doesn't seem to be a mechanism for removing existing properties.

Changing it to e.g. a dictionary property could make the dictionary overridable, e.g.:

[autoload]

autoloads={
  "AutoloadOverride": "*res://autoload_override.gd",
  "Autoload1": "*res://autoload_1.gd",
  "Autoload2": "*res://autoload_2.gd",
}

But that's indeed material for a feature proposal, so we can discuss possible solutions and implement the best one.

A change like this will probably be the easiest to implement, but other ways of "inserting" an autoload (or any script that can run before everything starts) into an existing game would be greatly appreciated.

Let me know what you think

[Qubus0]

If we can come to a conclusion on how to implement it, I am completely willing to give it a try myself, even though i've never done something like this before - but that's just experience waiting to be gathered, right? ;)