Fix SCRIPT ERROR/ERROR/WARNING on test output

Also "fixing" some GDScript completion tests which
where named wrongly.

modules/gdscript/tests/scripts/completion/argument_options/play_inferred.gd

@@ -1,3 +1,5 @@
+extends Node
+
 @onready var anim := $AnimationPlayer
 
 func test():

modules/gdscript/tests/scripts/completion/argument_options/play_typed.gd

@@ -1,3 +1,5 @@
+extends Node
+
 @onready var anim: AnimationPlayer = $AnimationPlayer
 
 func test():

modules/gdscript/tests/scripts/completion/argument_options/play_untyped.gd

@@ -1,3 +1,5 @@
+extends Node
+
 @onready var anim = $AnimationPlayer
 
 func test():

modules/gdscript/tests/scripts/completion/get_node/literal/dollar.gd

@@ -1,5 +1,5 @@
 extends Node
 
 func a():
-    %AnimationPlayer.➡
+    $UniqueAnimationPlayer.➡
     pass

modules/gdscript/tests/scripts/completion/get_node/literal/percent.gd

@@ -1,5 +1,5 @@
 extends Node
 
 func a():
-    $UniqueAnimationPlayer.➡
+    %AnimationPlayer.➡
     pass

modules/gdscript/tests/scripts/completion/get_node/member_inferred_scene/class_member_inferred_scene.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test := $A
+@onready var test := $A
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_inferred_scene/native_member_inferred_scene.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test := $AnimationPlayer
+@onready var test := $AnimationPlayer
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_scene/class_member_scene.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test = $A
+@onready var test = $A
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_scene/native_member_scene.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test = $AnimationPlayer
+@onready var test = $AnimationPlayer
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_typehint_scene/native_member_typehint_scene.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test: AnimationPlayer = $AnimationPlayer
+@onready var test: AnimationPlayer = $AnimationPlayer
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_typehint_scene_broad/class_member_typehint_scene_broad.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test: Node = $A
+@onready var test: Node = $A
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_typehint_scene_broad/native_member_typehint_scene_broad.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test: Node = $AnimationPlayer
+@onready var test: Node = $AnimationPlayer
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_typehint_scene_incompatible/class_member_typehint_scene_incompatible.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test: Area2D = $A
+@onready var test: Area2D = $A
 
 func a():
     test.➡

modules/gdscript/tests/scripts/completion/get_node/member_typehint_scene_incompatible/native_member_typehint_scene_incompatible.gd

@@ -1,6 +1,6 @@
 extends Node
 
-var test: Area2D = $AnimationPlayer
+@onready var test: Area2D = $AnimationPlayer
 
 func a():
     test.➡