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.Shared/Tag/TagComponent.cs

@@ -3,11 +3,12 @@ using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom.Prototy
 
 namespace Content.Shared.Tag
 {
-    [RegisterComponent, Friend(typeof(TagSystem))]
+    [RegisterComponent, Access(typeof(TagSystem))]
     public sealed class TagComponent : Component, ISerializationHooks
     {
         [ViewVariables]
         [DataField("tags", customTypeSerializer: typeof(PrototypeIdHashSetSerializer<TagPrototype>))]
+        [Access(typeof(TagSystem), Other = AccessPermissions.ReadExecute)] // FIXME Friends
         public readonly HashSet<string> Tags = new();
     }
 }