Include the ancestor field ast in the resolver's `ResolveInfo`

Just as how `field_asts` contains the descendants to be resolved after a resolver, it would be nice if the `ResolveInfo` object also contains the field ast's ancestors that leads to the currently-resolved field.

This information would make https://github.com/graphql-python/graphql-core/issues/127 really easy to resolve.

Empieza rastreando la definición de ResolveInfo y la población existente de field_asts a través del recorrido del resolver. Añade acceso a los ASTs antecesores del campo actual y, después, verifica que ResolveInfo exponga la cadena de antecesores esperada y que el caso de uso del issue 127 relacionado pueda obtenerla.

Escrito por el modelo de indexación a partir del texto del issue.