Widget Rebuild Stats - add animating rebuild indicators

In IntelliJ, we had little animating spinners when a widget was rebuilding. In the DevTools version, the count increases, but we don't have an indicator to draw the eye to the rebuilding widget

Start by locating the Widget Rebuild Stats view and the code that displays its rebuild count, then compare the current behavior with the issue screenshot and IntelliJ's rebuild indicator. Done means a widget that is rebuilding has a visible animated indicator that draws attention while the rebuild is occurring.

Scritto dal modello di indicizzazione a partire dal testo della issue.