Adds region hierarchy in templates (#14213)

* initial work to render hierarchical region #13735

* adds site display #13735

* cleanup #13735

* adds display region tag #13735

* refactored region hierarchy #13735

* refactored region hierarchy #13735

* renamed display_region to nested_tree #13735

* Make render_tree suitable for generic use

* Remove errant item from __all__

---------

Co-authored-by: Jeremy Stretch <jstretch@netboxlabs.com>

netbox/utilities/templatetags/mptt.py

@@ -0,0 +1,20 @@
+from django import template
+from django.utils.safestring import mark_safe
+
+register = template.Library()
+
+
+@register.simple_tag()
+def nested_tree(obj):
+    """
+    Renders the entire hierarchy of a recursively-nested object (such as Region or SiteGroup).
+    """
+    if not obj:
+        return mark_safe('—')
+
+    nodes = obj.get_ancestors(include_self=True)
+    return mark_safe(
+        ' / '.join(
+            f'<a href="{node.get_absolute_url()}">{node}</a>' for node in nodes
+        )
+    )