Transform Revert button into discard changes

Having a revert button in Designer that has a totally different behavior than the discard changes button in Modeler is confusing for users.

With NXS-4516, it is important that we allow a way to discard changes instead of erasing everything: if people switch elements they might want to reset their changes if they do a mistake.

TODO
If technically possible

• the revert button in layouts should be renamed to Discard Changes and reset changes => revert will still be possible from the layouts listing
• for UI components except dashboard remove button should similarly be renamed to Discard Changes and reset changes in the form => remove will still be possible from the listing
• for dashboard
  • the revert button should be kept as there is no way to revert it otherwise
  • a Discard Changes button should be added to reset changes
  • buttons order (left to right): Revert, Discard Changes, Save

If not technically possible then the revert / remove button should be removed except for the dashboard.