Reimplement GameConfigController window sizing and centering

[miketvo]

Will be possible when this proposal goes through and its PR gets merged: godotengine/godot-proposals#6247

Current workaround:

func _ready() -> void:
    # Set window size and center window for desktop devices.
    if Global.os_platform == "Desktop":
        # Workaround for:
        # https://github.com/godotengine/godot-proposals/issues/6247.
        # TODO: Reimplement this when there is better support for the above
        # issue in future Godot 4.x versions.
        var window: Window = get_window()
        window.size = GameConfig.RESOLUTIONS[GameConfig.config.graphics.resolution]
        @warning_ignore("integer_division")
        window.position = Vector2i(
                int(get_viewport_rect().size.x / 2) - window.size.x / 2,
                int(get_viewport_rect().size.y / 2) - window.size.y / 2
        )

Affects all projects in the repository.