Can't use EditorPlugin.add_autoload_singleton() with a relative path

[sosasees]

Godot version

4.0.3.stable

System information

Linux/X11

Issue description

when creating addons, i want to use relative paths so that things don't break if i (or another user) decides to rename and/or move the add-on's folder.

using relative paths with add_autoload_singleton() doesn't work because of an error when enabling the add-on.

res://addons/my_plugin/plugin.gd

@tool
extends EditorPlugin


func _enter_tree():
	# this line doesn't work:
	add_autoload_singleton('MyAutoload', 'my_autoload.gd')
	# these lines work:
	#add_autoload_singleton( 'MyAutoload',
	#	'res://addons/my_plugin/my_autoload.gd'
	#)


func _exit_tree():
	remove_autoload_singleton('MyAutoload')

error message window when enabling the add-on

┌─────────────────────────────────────────────────┐
│ Warning!                                  _ □ X │
├─────────────────────────────────────────────────┤
│ Can't add Autoload:                             │
│ res:// is an invalid path. File does not exist. │
│                                                 │
│              [OK]      [Copy Text]              │
└─────────────────────────────────────────────────┘

the add-on does not get disabled because of the error.
the error-free parts of the add-on still get activated, just the autoload doesn't get created.

Steps to reproduce

1. create a plugin with the subfolder "my_plugin" and script name "plugin.gd"
2. create an empty script in res://addons/my_plugin/my_autoload.gd
3. edit res://addons/my_plugin/plugin.gd:

@tool
extends EditorPlugin


func _enter_tree():
	add_autoload_singleton('MyAutoload', 'my_autoload.gd')


func _exit_tree():
	remove_autoload_singleton('MyAutoload')

4. enable the plugin
5. see the error message window

Minimal reproduction project

add_autoload_singleton.zip
(13.9 KiByte download, 11.4 KiByte unzipped)