[multi-asic] BBR support on internal-peers for multi-asic platfroms. (#6848)

Enable BBR config allowas-in 1 for internal peers

Why I did:
To advertise BBR routes learnt via e-BGP peer in one asic/namespace to another iBGP asic/namespace via Route Reflector.

dockers/docker-fpm-frr/frr/bgpd/templates/internal/instance.conf.j2

@@ -28,6 +28,7 @@
 !
     neighbor {{ neighbor_addr }} next-hop-self force
 !
+    neighbor {{ neighbor_addr }} allowas-in 1
     neighbor {{ neighbor_addr }} activate
   exit-address-family
 !

src/sonic-bgpcfgd/tests/data/internal/instance.conf/result_back_v4.conf

@@ -9,6 +9,7 @@
     neighbor 10.10.10.10 route-map FROM_BGP_INTERNAL_PEER_V4 in
     neighbor 10.10.10.10 route-reflector-client
     neighbor 10.10.10.10 next-hop-self force
+    neighbor 10.10.10.10 allowas-in 1
     neighbor 10.10.10.10 activate
   exit-address-family
 !

src/sonic-bgpcfgd/tests/data/internal/instance.conf/result_back_v6.conf

@@ -9,6 +9,7 @@
     neighbor fc::10 route-map FROM_BGP_INTERNAL_PEER_V6 in
     neighbor fc::10 route-reflector-client
     neighbor fc::10 next-hop-self force
+    neighbor fc::10 allowas-in 1
     neighbor fc::10 activate
   exit-address-family
 !

src/sonic-bgpcfgd/tests/data/internal/instance.conf/result_front_v4.conf

@@ -7,6 +7,7 @@
   address-family ipv4
     neighbor 10.10.10.10 peer-group INTERNAL_PEER_V4
     neighbor 10.10.10.10 next-hop-self force
+    neighbor 10.10.10.10 allowas-in 1
     neighbor 10.10.10.10 activate
   exit-address-family
 !

src/sonic-bgpcfgd/tests/data/internal/instance.conf/result_front_v6.conf

@@ -7,6 +7,7 @@
   address-family ipv6
     neighbor fc::10 peer-group INTERNAL_PEER_V6
     neighbor fc::10 next-hop-self force
+    neighbor fc::10 allowas-in 1
     neighbor fc::10 activate
   exit-address-family
 !