Update analytics dashboard available visualizations

What does this MR do and why?

This MR updates AnalyticsDashboard to fetch the available visualisations from the backend added in Create visualizations GraphQL endpoint (#411597 - closed). This is part of a larger change to migrate the dashboard designer to Snowplow. Snowplow migration for dashboard & visualizatio... (&10758 - closed)

This MR does not:

• Remove the deprecated Jitsu methods or code.
  • That will be removed in Remove Jitsu-related frontend code from Product... (#406660 - closed).

Known issues:

• Creating a visualization using the designer causes a 500 on the dashboard designer.
  • This will be resolved in Remove title property and update the slug to th... (#415467 - closed).
  • Workaround: If you do this, then you'll need to delete the newly created visualization file in the repository.
• Adding a snowplow panel results in an error.
  • This is blocked by [Dashboard designer] Save dehydrated dashboard ... (#414283 - closed).
    • This will add a new method of modifying the Apollo client cache to update the immutable dashboard state.

Note: This feature is experimental and not intended for users. It is hidden behind multiple default off feature flags.

Screenshots or screen recordings

Before	After

Before the visualization selector would be stuck in loading (it would never actually load).

How to set up and validate locally

1. Make sure you are on GitLab Ultimate
2. Follow these instructions to set up Product Analytics in your GDK.
   • NB enable both the product_analytics_snowplow_support and combined_analytics_dashboards_editor feature flags.
3. Create a new project with an empty repository.
4. Enable custom dashboards at Project > Settings > Analytics and pick the empty project.
5. Click on New dashboard button and verify that the list of available visualizations load.

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.

Related to #414281 (closed)