Introduced the support for `chunkId` in FE

What does this MR do and why?

Introduces the support for streaming in frontend

#419531 (closed)

Screenshots or screen recordings

Without FF	With FF
streaming-example-no-ff	streaming-example

How to set up and validate locally

1. Enable AI features https://docs.gitlab.com/ee/development/ai_features/index.html#test-ai-features-locally
2. Enable the FF: Feature.enable(:stream_gitlab_duo)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.