Moves HumanoidAppearanceComponent to ECS (#4855)

* Moves HumanoidCharacterAppearance to ECS

* Makes HumanoidAppearanceSystem work over networks

* Makes HumanoidAppearanceSystem more efficient

* Cleans up the files

* Updates privacy on a couple of functions

* Fixes a few using references, renames a file

* Makes HumanoidAppearanceSystem more cleaner

* Fixes Magic Mirror

* Cleanup

* HumanoidAppearanceComponent now has a friend

SharedHumanoidAppearanceSystem is only allowed to act on this, now

* Fixes the Body-HumanoidAppearance ECS scaffolding

* a little cleanup never hurt anybody

* quick fix for magic mirror appearance access

* Replaces a networked event with a local one

This one was... causing bugs

Content.Shared/Body/Part/IBodyPartAdded.cs

@@ -1,5 +1,6 @@
 using System;
 using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization;
 
 namespace Content.Shared.Body.Part
 {
@@ -17,6 +18,8 @@ namespace Content.Shared.Body.Part
         void BodyPartAdded(BodyPartAddedEventArgs args);
     }
 
+
+    [Serializable, NetSerializable]
     public class BodyPartAddedEventArgs : EventArgs
     {
         public BodyPartAddedEventArgs(string slot, SharedBodyPartComponent part)