EZP-23583: As an editor, I want to be able to use forms in the administration part of the PlatformUI App

JIRA: https://jira.ez.no/browse/EZP-23583

# Description

This patch adds the JS code so that the forms are handled in the admin part, ie you are not redirected anymore on those unstyled "pages" :-)

Screencast of the creation and the removal of a section: https://www.youtube.com/watch?v=8Nxa1kaN0gU

## Known issue / Limitation

* [EZP-23700](https://jira.ez.no/browse/EZP-23700): after a form submission the PlatformUI should redirect to a different URL provided the form response

# Tests

manual tests + unit tests