Add identifiers field in CreationPersonType and handle on_create logic in PersonIdentifiersType

- Introduce `identifiers` field to `CreationPersonType` with a dedicated form type.
- Update `PersonIdentifiersType` to support `step` option (`on_create` and `on_edit`).
- Skip certain identifiers in `on_create` step based on presence configuration.
- Adjust Twig template to display `identifiers` conditionally.

src/Bundle/ChillPersonBundle/Resources/views/Person/create.html.twig

@@ -88,6 +88,15 @@
             <div data-suggest-container="{{ altName.vars.full_name|e('html_attr') }}" class="col-sm-8" style="margin-left: auto;"></div>
         {% endfor %}
     {% endif %}
+    {% if form.identifiers|length > 0 %}
+        {% for f in form.identifiers %}
+            <div class="row mb-1" style="display:flex;">
+                {{ form_row(f) }}
+            </div>
+        {% endfor %}
+    {% else %}
+        {{ form_widget(form.identifiers) }}
+    {% endif %}
 
     {{ form_row(form.gender, { 'label' : 'Gender'|trans }) }}