Add element IDs to dialog title and subtitle texts

This allows us to easily replace just the text based on a server response using TeleportController

Ideally, the {{ id }} should be a prefix instead of a postfix, but there's an existing title-{{ id }} for the h2 element so we follow it for now

wagtail/admin/templates/wagtailadmin/shared/dialog/dialog.html

@@ -33,11 +33,11 @@
                     <h2 class="w-dialog__title w-h1" id="title-{{ id }}">
                         {% fragment as icon_classname %}{% classnames "w-dialog__icon" icon_classname %}{% endfragment %}
                         {% if icon_name %}{% icon name=icon_name classname=icon_classname %}{% endif %}
-                        {{ title }}
+                        <span id="title-text-{{ id }}">{{ title }}</span>
                     </h2>
 
                     {% if subtitle %}
-                        <p class="w-dialog__subtitle w-help-text">{{ subtitle }}</p>
+                        <p class="w-dialog__subtitle w-help-text" id="subtitle-{{ id }}">{{ subtitle }}</p>
                     {% endif %}
                 </div>