Response streaming support for Python runtime

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**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**
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L’issue ne nomme aucun fichier d’implémentation, test ou point d’entrée. Commencez par examiner la prise en charge existante du streaming des réponses dans Node.js et l’architecture du runtime Python ; le travail sera terminé lorsque les runtimes Python pourront diffuser progressivement les réponses Lambda aux clients avec une prise en charge équivalente.

Rédigé par le modèle d'indexation à partir du texte de l'issue.