Refactor body component to use slots instead of an army of dictionaries (#3749)

* Refactor body component to use slots instead of an army of dictionaries

* Update vox

* Replace static method call with extension

* Add setpart method, replace dispose with shutdown

* Fix tests, fix not listening to slot events when setting a part

Content.Server/Commands/Body/AddHandCommand.cs

@@ -138,11 +138,9 @@ namespace Content.Server.Commands.Body
             }
 
             var slot = part.GetHashCode().ToString();
-            var response = body.TryAddPart(slot, part, true)
-                ? $"Added hand to entity {entity.Name}"
-                : $"Error occurred trying to add a hand to entity {entity.Name}";
+            body.SetPart(slot, part);
 
-            shell.WriteLine(response);
+            shell.WriteLine($"Added hand to entity {entity.Name}");
         }
     }
 }