Form Builder submission handler is not really well working when the form is render in an ESI. (which is totally valid)

Lhe listener is on the `MVCEvents::PRE_CONTENT_VIEW`
which is inside called inside the ESI. But the ESI does not have the `POST` then for eZ the Form was never submitted.

I think the listener should not be on the `MVCEvents::PRE_CONTENT_VIEW` but on the request so it is handle differently…

My use case was that I am using a form in the footer. (newsletter registration)
=> This is on an Enterprise project obviously.