Edit: This PR has been replaced with #67714
Edit: Currently not working as intended. Will post updates.

This simple PR makes it possible to use cyclic references with preloaded scripts.

After trying to load completely a script using ResourceLoader::load() (that calls down the line ResourceFormatLoaderGDScript::load() then right after GDScriptCache::get_full_script()), if the reference is null (which means that the script is not yet compiled), then we use instead the GDScriptCache::get_shallow_script().

The beauty of GDScriptCache::get_shallow_script() is that it gives back the result of GDScriptCache::get_full_script() if it has been fully loaded once.

So, this code works with this PR, which returns this error on master: Constant value uses script from "res://b.gd" which is loaded but not compiled.:

# main.gd
const A = preload("res://a.gd")

func _ready() -> void:
	A.hello()  # The console will print: "A.HELLO_WORLD: hello, world!"

# a.gd
extends Node

const B = preload("res://b.gd")

const HELLO_WORLD: = "hello, world!"

static func test() -> void:
	B.test()

# b.gd
extends Node

const A = preload("res://a.gd")

static func test() -> void:
	prints("A.HELLO_WORLD:", A.HELLO_WORLD)

Minimal reproduction project:
cyclic3.zip

Fixes #58181, fixes #61043, fixes #32165