Property tracker loosing track on GraphQL abstract defs

[Horusiath]

Problem here is lose coupling between GraphQL interfaces and .net types - you can have i.e. GraphQL interface Node(fields: [ id: Node -> ID ]) that maps directly to System.Object on .NET side - pattern often used for Relay. This messes up with property tracker joining phase as it will pass over, if parent type was simply an object. Therefore this part needs to correctly work with abstract defs - possibly as a special-case scenario.