feat(vpn): Add search index for TunnelGroup

Introduces `TunnelGroupIndex` for enabling search functionality on
Tunnel Groups. Includes searchable fields for `name` and `description`
with respective weights and display attributes.

Closes #20237

netbox/vpn/search.py

@@ -14,6 +14,17 @@ class TunnelIndex(SearchIndex):
     display_attrs = ('group', 'status', 'encapsulation', 'tenant', 'tunnel_id', 'description')
 
 
+@register_search
+class TunnelGroupIndex(SearchIndex):
+    model = models.TunnelGroup
+    fields = (
+        ('name', 100),
+        ('slug', 110),
+        ('description', 500),
+    )
+    display_attrs = ('description',)
+
+
 @register_search
 class IKEProposalIndex(SearchIndex):
     model = models.IKEProposal