Make script annotations placed before class_name and extends

modules/gdscript/tests/scripts/parser/errors/class_name_after_annotation.gd

@@ -1,6 +1,6 @@
-# Error here. `class_name` should be used *before* annotations, not after (except @tool).
-@icon("res://path/to/optional/icon.svg")
+# Error here. Annotations should be used before `class_name`, not after.
 class_name HelloWorld
+@icon("res://path/to/optional/icon.svg")
 
 func test():
     pass

modules/gdscript/tests/scripts/parser/errors/class_name_after_annotation.out

@@ -1,2 +1,2 @@
 GDTEST_PARSER_ERROR
-"class_name" should be used before annotations (except @tool).
+Annotation "@icon" is not allowed in this level.

modules/gdscript/tests/scripts/parser/features/class_name.gd

@@ -1,5 +1,5 @@
-class_name HelloWorld
 @icon("res://path/to/optional/icon.svg")
+class_name HelloWorld
 
 func test():
 	pass