Preload and cache the Task when hovering a link in the tasks list

Currently, we start loading the task only when the task modal is open. We could improve UX by pre-loading the work item on hover: when the user hovers the task link for more than 150 ms, we start fetching the data, and then we populate the modal with task data immediately.

Also, it would be nice to have the task cached after we fetched it for the first time.