Refactor GDScript/C# script templates logic to be editor-only

Not a full refactor as it still goes through ScriptLanguage so it's hacky,
but at least it can now compile without this.

modules/gdscript/editor/script_templates/EditorScript/basic_editor_script.gd

@@ -0,0 +1,8 @@
+# meta-description: Basic editor script template
+@tool
+extends EditorScript
+
+
+# Called when the script is executed (using File -> Run in Script Editor).
+func _run() -> void:
+	pass