Explicit input instantiation escape hatch

**Is your feature request related to a problem? Please describe.**

I'm designing a stable external API that needs to wrap our existing fast-moving internal API. Sometimes, I want to call existing resolvers to do that.

However, when using deeply nested inputs with a `@property`, it's not possible to wrap that input with another (simplified) input, because I can't create an "instance" with the correct parameters on creation.

**Describe the solution you'd like**
I would like an escape hatch to instantiate inputs.

**Describe alternatives you've considered**
An inheritance-based mechanism where I could remove fields and structures from a parent might solve the problem, but I don't think it would be as clean.

No se nombran archivos, pruebas ni puntos de entrada. Aclara la API prevista para la instanciación de inputs, especialmente cómo deben comportarse los inputs profundamente anidados y los campos @property, y después identifica las rutas existentes de construcción de inputs y de resolvers que se deben inspeccionar. La finalización debe incluir un escape hatch definido y cobertura para el caso de uso de wrapping.

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