Enable optimistic prefetching for work items in issuable list

What does this MR do and why?

This MR enables optimistic prefetching of a Work Item when hovering on a linked issue, allowing for a more seamless experience for users.

Apollo caches query's response, so when Work Item drawer opens the data is already available.

Prefetching is being triggered after 250ms of hovering over a linked work item.

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

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Screen_Recording_2024-07-15_at_3.47.38_PM

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Make sure the issues_list_drawer feature flag is enabled
2. Visit /issues page in a project of your choice
3. Hover over any issue on the list for at least 250ms, open the issue and make sure that the loading state is not visible in the work item drawer
4. Check the network tab to make sure the query only happens once on hover
5. Test other issues with quickly removing your mouse from the work item link and make sure the query is not triggered

Related to #471083 (closed)