AnnotatedCreatorCollector avoids processing synthetic methods

This implementation matches the AnnotatedMethodCollector which
also avoids synthetic methods. In the debugger I found most
iterations through _findPotentialFactories were checking synthetic
methods rather than human-declared methods.

Author: carterkozak

src/main/java/com/fasterxml/jackson/databind/introspect/AnnotatedCreatorCollector.java

@@ -207,7 +207,7 @@ private List<AnnotatedMethod> _findPotentialFactories(JavaType type, Class<?> pr
 
         // First find all potentially relevant static methods
         for (Method m : ClassUtil.getClassMethods(type.getRawClass())) {
-            if (!Modifier.isStatic(m.getModifiers())) {
+            if (!_isIncludableFactoryMethod(m)) {
                 continue;
             }
             // all factory methods are fine:
@@ -242,7 +242,7 @@ private List<AnnotatedMethod> _findPotentialFactories(JavaType type, Class<?> pr
         if (primaryMixIn != null) {
             MemberKey[] methodKeys = null;
             for (Method mixinFactory : primaryMixIn.getDeclaredMethods()) {
-                if (!Modifier.isStatic(mixinFactory.getModifiers())) {
+                if (!_isIncludableFactoryMethod(mixinFactory)) {
                     continue;
                 }
                 if (methodKeys == null) {
@@ -274,6 +274,14 @@ private List<AnnotatedMethod> _findPotentialFactories(JavaType type, Class<?> pr
         return result;
     }
 
+    private boolean _isIncludableFactoryMethod(Method m)
+    {
+        return Modifier.isStatic(m.getModifiers())
+                // 09-Nov-2020, ckozak: Avoid considering synthetic methods such as
+                // lambdas used within methods because they're not relevant.
+                && !m.isSynthetic();
+    }
+
     protected AnnotatedConstructor constructDefaultConstructor(ClassUtil.Ctor ctor,
             ClassUtil.Ctor mixin)
     {