Before this revision, it was not possible to display a chatter inside a <sheet>.
As the chatter is reused (when switching in edit, records, etc.), it is detached
(to keep its handlers) before updating the form $el.
The problem here is that the chatter was detached in `_updateView` from
`$form.contents()` where the chatter is a root element ; when setting the form
view html, the chatter was thus still present. This was thus only working
correctly if the chatter was a direct child of <form>.
To keep it displayed in all cases, we now detach it at the chatter node
rendering.
Closes#20032
Martin Geubelle
e63c550ed1