Support subscriptions in GraphQL explorer

What does this MR do and why?

This loads the graphiql library directly from the NPM package and forgoes the use of the graphiql-rails gem so that we can customize the fetcher to support subscriptions.

This uses a custom fetcher that uses our Apollo client so that it supports subscriptions

Related to #23102 (closed)

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

Screen_Recording_2024-07-04_at_5.15.24_PM

How to set up and validate locally

1. Switch to this MR branch and run yarn to install the new dependencies
2. Visit /-/graphql-explorer
3. Test out a subscription