Simpler check to avoid primitive conversion in ConvertingPropertyAccessor.

We now use Spring's ClassUtils.isAssignable(…) directly. Unit tests to verify that conversion is skipped for primitive / boxed scenarios.

See #2546.

src/main/java/org/springframework/data/mapping/model/ConvertingPropertyAccessor.java

@@ -104,7 +104,7 @@ public class ConvertingPropertyAccessor<T> extends SimplePersistentPropertyPathA
 
 		return (S) (source == null //
 				? null //
-				: ClassUtils.resolvePrimitiveIfNecessary(type).isAssignableFrom(source.getClass()) //
+				: ClassUtils.isAssignable(type, source.getClass())
 						? source //
 						: conversionService.convert(source, type));
 	}