OpenAPIDeserializer.getSchema: Handle "enum" correctly when schema type is "array" or "object"

[kerrykimbrough]

Fixes issue #1419

For a schema of type array, each element of the enum array must be an array. But an enumerated array may contain values that don't have a native Java representation (for example, "object" values). Therefore, an enumerated array element is represented by an ArrayNode value, which contains the fully-parsed representation of the enumerated value.

Similarly, for a schema of type object, each element of the enum array must be an object. But an object value doesn't have a well-defined native Java representation. Therefore, an enumerated object element is represented by an ObjectNode.

But in any case, a null element of an enum array is represented by a Java null value, which is consistent with enum handling for all other schema types.

[gracekarina]

thanks @kerrykimbrough