Refactor serialization copying to use source generators (#19412)

Content.Shared/Body/Components/BodyComponent.cs

@@ -9,10 +9,10 @@ namespace Content.Shared.Body.Components;
 
 [RegisterComponent, NetworkedComponent]
 [Access(typeof(SharedBodySystem))]
-public sealed class BodyComponent : Component
+public sealed partial class BodyComponent : Component
 {
     [DataField("prototype", customTypeSerializer: typeof(PrototypeIdSerializer<BodyPrototype>))]
-    public readonly string? Prototype;
+    public string? Prototype;
 
     [DataField("root")]
     public BodyPartSlot? Root;