Returning deeply extended type from inteface query

[MichalLytek]

#279 added support for returning plain object from queries which returns type is an interface but it introduced a regression that makes interfaces-inheritance example not working correctly.

The implementingObjectTypesTargets looks for classes that implements selected interface but because of current pipeline limitation (#183) it doesn't have access to parent and its parent classes metadata, so when using deeply nested inheritance, it might return the first (base) class always.

The workaround for now is to use custom resolveType functions.