Response streaming support for Python runtime

**Note**
> * Please vote on this issue by adding a 👍 reaction to the original issue to help the community and maintainers prioritize this request
> * Please do not leave "+1" or "me too" comments, they generate extra noise for issue followers and do * not help prioritize the request
> If you are interested in providing additional feedback, please leave a comment

**Description**
Lambda response streaming allows you to incremental stream responses back to clients rather than waiting for the entire response to be buffered first, reducing Time to First Byte. It is currently only supported for Node.js runtime. We would expand support for response streaming to Python runtimes.

**Additional context**
Add additional context here

El issue no nombra archivos de implementación, tests ni puntos de entrada. Empieza revisando la compatibilidad existente con el streaming de respuestas en Node.js y la arquitectura del runtime de Python; el trabajo estará terminado cuando los runtimes de Python puedan transmitir incrementalmente las respuestas de Lambda a los clientes con una compatibilidad equivalente.

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