As a WWT user, I only want the loading animation in the revision details pop-up displayed when data is loading, so I am not inconvenienced with unnecessary wait time or loading states.
Background: The loading animation, as implemented in T231115, is displayed when we ask the MediaWiki API for the revision summary; it has a caveat of being delayed a bit so it does not appear too jumpy even if the connection is super fast. However, if we reopen a popup that was previously opened, we already have the data to display and there's no need to show the animation again.
**Acceptance criteria**
* When opening the revision popup, show loading animation (as exists right now) for loading data
* When reopening a popup that was previously opened (and data is already available) show the data immediately without the loading animation.