Supporting multiple dynamic forms on the same page

[dev-newvisibility]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	yes
Deprecations?	no
License	MIT

What's in this PR?

This PR replaces the URL parameter send=true that is added when a form is submitted with send=<form-id>

Why?

At the moment, if you add multiple dynamic forms to the same template, or if multiple forms are displayed on the same page, you can't know which one has been submitted due to the fact that the send URL parameter value is the same for all forms.

Example Usage

{% if app.request.get('send') != view.form.entity.formId %}
  {# FORM THEME #}
  {% form_theme content.form '@SuluForm/themes/basic.html.twig' %}
  {{ form(content.form) }}
{% else %}
  {{ view.form.entity.successText|raw }}
{% endif %}

BC Breaks/Deprecations

Templates must be updated