PIM-2574: No popup saying there is unsaved changes

When a product form is submitted with invalid values, the page in
reloaded with theses values (even the good one) and if we click on back
to the grid there is no warning message we are leaving a form with
unsaved values

| Q                    | A
| -------------------- | ---
| Bug fix?             | Yes
| New feature?         | No
| BC breaks?           | No
| CI currently passes? | ?
| Tests pass?          | Yes
| Scenarios pass?      | ?
| Checkstyle issues?*  | No
| PMD issues?**        | No
| Changelog updated?   | Yes
| Fixed tickets        | PIM-2574
| Doc PR               | No
The title of the scenario should describe the thing you want to be able to do, not the action that will be performed, like "Display a message when form submission fails and I try to leave the page", not "Edit product, save and return to grid". This would be fine if the scenario was checking if returning to grid works :)