Enable BFD for Static Route for chassis-packet. (#15383)

*What I did:
Enable BFD for Static Route for chassis-packet. This will trigger the use of the feature as defined in here: #13789

Signed-off-by: Abhishek Dosi <abdosi@microsoft.com>

src/sonic-config-engine/minigraph.py

@@ -1986,6 +1986,10 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None, hw
             port['mux_cable'] = "true"
 
     if static_routes:
+        # Enable static Route BFD by default for static route in chassis-packet
+        if switch_type == "chassis-packet":
+            for pfx, data in static_routes.items():
+                data.update({"bfd":"true"})
         results['STATIC_ROUTE'] = static_routes
 
     for nghbr in list(neighbors.keys()):

src/sonic-config-engine/tests/test_cfggen.py

@@ -1029,14 +1029,14 @@ def test_minigraph_bgp_packet_chassis_static_route(self):
         output = self.run_script(argument)
         self.assertEqual(
             utils.to_dict(output.strip()),
-            utils.to_dict("{'8.0.0.1/32': {'nexthop': '192.168.1.2,192.168.2.2', 'ifname': 'PortChannel40,PortChannel50', 'advertise':'false'}}")
+            utils.to_dict("{'8.0.0.1/32': {'nexthop': '192.168.1.2,192.168.2.2', 'ifname': 'PortChannel40,PortChannel50', 'advertise':'false', 'bfd':'true'}}")
         )
 
         argument = ['-m', self.packet_chassis_graph, '-p', self.packet_chassis_port_ini, '-n', "asic1", '-v', "STATIC_ROUTE"]
         output = self.run_script(argument)
         self.assertEqual(
             utils.to_dict(output.strip()),
-            utils.to_dict("{'8.0.0.1/32': {'nexthop': '192.168.1.2,192.168.2.2', 'ifname': 'PortChannel40,PortChannel50', 'advertise':'false'}}")
+            utils.to_dict("{'8.0.0.1/32': {'nexthop': '192.168.1.2,192.168.2.2', 'ifname': 'PortChannel40,PortChannel50', 'advertise':'false', 'bfd':'true'}}")
         )
 
     def test_minigraph_bgp_packet_chassis_vlan_subintf(self):

src/sonic-yang-models/yang-models/sonic-static-route.yang

@@ -54,6 +54,12 @@ module sonic-static-route {
           }
           default "false";
         }
+        leaf bfd {
+          type string {
+            pattern "((true|false),)*(true|false)";
+          }
+          default "false";
+        }
       }
       list STATIC_ROUTE_LIST {
         key "vrf_name prefix";