Rename 'icon' context variable to avoid leaking into shared/field.html

wagtail/admin/templates/wagtailadmin/generic/chooser/chooser.html

@@ -1,5 +1,5 @@
 {% load i18n wagtailadmin_tags %}
-{% include "wagtailadmin/shared/header.html" with title=page_title merged=1 icon=icon %}
+{% include "wagtailadmin/shared/header.html" with title=page_title merged=1 icon=header_icon %}
 
 <div class="w-tabs" data-tabs data-tabs-disable-url>
     <div class="tab-content nice-padding">

wagtail/admin/views/generic/chooser.py

@@ -23,7 +23,7 @@ class ModalPageFurnitureMixin(ContextMixin):
         context = super().get_context_data(**kwargs)
         context.update(
             {
-                "icon": self.icon,
+                "header_icon": self.icon,
                 "page_title": self.page_title,
             }
         )