feat: switch character prefab to variant of another prefab

Author: rYuuk

Samples~/AvatarControl/Avatar Control.unity

@@ -1262,7 +1262,7 @@ MonoBehaviour:
   NetworkConfig:
     ProtocolVersion: 0
     NetworkTransport: {fileID: 1754146316}
-    PlayerPrefab: {fileID: 1192642991364198764, guid: 706d489d79a06dd4cadf68ab0c52f392, type: 3}
+    PlayerPrefab: {fileID: 918681697409016310, guid: 39bfa80ee51e22c4b9b3847156eb4def, type: 3}
     Prefabs:
       NetworkPrefabsLists:
       - {fileID: 11400000, guid: 8c66e821e14565f40a0c65c9a7bac000, type: 2}

Samples~/AvatarControl/NetworkPrefabs-45480.asset

@@ -15,7 +15,7 @@ MonoBehaviour:
   IsDefault: 0
   List:
   - Override: 0
-    Prefab: {fileID: 1192642991364198764, guid: 706d489d79a06dd4cadf68ab0c52f392, type: 3}
+    Prefab: {fileID: 918681697409016310, guid: 39bfa80ee51e22c4b9b3847156eb4def, type: 3}
     SourcePrefabToOverride: {fileID: 0}
     SourceHashToOverride: 0
     OverridingTargetPrefab: {fileID: 0}