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**
Add additional context here

Nell’issue non sono indicati file di implementazione, test o punti di ingresso. Inizia esaminando il supporto esistente per lo streaming delle risposte in Node.js e l’architettura del runtime Python; il lavoro sarà completato quando i runtime Python potranno trasmettere in streaming in modo incrementale le risposte Lambda ai client con un supporto equivalente.

Scritto dal modello di indicizzazione a partire dal testo della issue.