backport[v16]: Implement OneOf Input Objects via `@oneOf` directive (#4124)
Co-authored-by: Erik Kessler <erik.kessler1@gmail.com>
Co-authored-by: Benedikt Franke <benedikt.franke@mll.com>
Co-authored-by: Michael Hayes <michael@hayes.io>
Co-authored-by: Mike Ciesielka <maciesielka@comcast.net>