Fields and forms redesign

The tab *Fields* on the vector layer properties dialog should be split into two different tabs that separate data-related from form- and widget-related user interface elements.

This is expected to improve user experience and usability.
I mean the GUI element with the small triangle to collapse/expand content e.g. in https://www.qgis.org/fr/_images/Selection_005.png (is that a collapsible group box?)