Fix some friend access violations by allowing others access. (#8594)

Rename Friend attribute to Access attribute.
Updates submodule to v0.21.0.0 as well.

Content.Server/Extinguisher/FireExtinguisherComponent.cs

@@ -3,7 +3,7 @@ using Content.Shared.Sound;
 namespace Content.Server.Extinguisher;
 
 [RegisterComponent]
-[Friend(typeof(FireExtinguisherSystem))]
+[Access(typeof(FireExtinguisherSystem))]
 public sealed class FireExtinguisherComponent : Component
 {
     [DataField("refillSound")] public SoundSpecifier RefillSound = new SoundPathSpecifier("/Audio/Effects/refill.ogg");