Refactor DuoChats Subscriptions on cancel

What does this MR do and why?

part of solving: #474242

Migration MR for: gitlab-ui!4498

This MR introduces the following changes:

• makes sure that the ClientSubscriptionID is unique for every prompt (was unique per component mount before)
• makes sure GraphQL Subscriptions are unsubscribed on prompt cancel
• removes passing cancelledRequestIds to the shared GitLab UI component

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

No visual changes, see a demo of the network tab, where you can see the Subscriptions being unsubscribed attached.

Before	After
2024-09-06_16-10-52	2024-09-06_16-07-53

How to set up and validate locally

1. Check out this GitLab UI branch and integrate it to your GDK using this guide.
2. Setup Duo Chat: https://docs.gitlab.com/ee/development/ai_features/duo_chat.html#set-up-gitlab-duo-chat
3. Make sure everything works as expected, answers are streaming in