Review data fetching and caching

[tomjeatt]

This should be a small task—we've made some changes to data fetching at the feature level (e.g. disabling refetch on window focus for XCM transfers), but we need to make sure we have a convention for how this is handled across the app, and apply it consistently as and when we refactor legacy features.

Also, consider updating react-query to the latest version 4.0 (link)