Fix two issues flagged in third AI code review

- MessagePackFactoryBuilder: deep-copy extTypeCustomDesers via copy constructor
  so rebuilt factories have independent deserializer state
- MessagePackDataformatForFieldIdTest: fix typo in test method name
  (testMixedKeysBackwardsCompatiable -> testMixedKeysBackwardsCompatible)

Author: komamitsu

msgpack-jackson3/src/main/java/org/msgpack/jackson/dataformat/MessagePackFactoryBuilder.java

@@ -47,7 +47,8 @@ public MessagePackFactoryBuilder(MessagePackFactory base)
         this.reuseResourceInGenerator = base.isReuseResourceInGenerator();
         this.reuseResourceInParser = base.isReuseResourceInParser();
         this.supportIntegerKeys = base.isSupportIntegerKeys();
-        this.extTypeCustomDesers = base.getExtTypeCustomDesers();
+        ExtensionTypeCustomDeserializers srcDesers = base.getExtTypeCustomDesers();
+        this.extTypeCustomDesers = srcDesers == null ? null : new ExtensionTypeCustomDeserializers(srcDesers);
     }
 
     public MessagePackFactoryBuilder packerConfig(MessagePack.PackerConfig config)

msgpack-jackson3/src/test/java/org/msgpack/jackson/dataformat/MessagePackDataformatForFieldIdTest.java

@@ -110,7 +110,7 @@ public void testMixedKeys()
     }
 
     @Test
-    public void testMixedKeysBackwardsCompatiable()
+    public void testMixedKeysBackwardsCompatible()
             throws IOException
     {
         ObjectMapper mapper = MessagePackMapper.builder(new MessagePackFactory())