EVPN Multi Home Support

[JaiOCP]

Host may be reachable via multiple VTEPs in the EVPN topology. In this case load balancing need to happen across VTEPs.

This is achieved using a new bridge port type SAI_BRIDGE_PORT_TYPE_BRIDGE_PORT_NEXT_HOP_GROUP that is going to use SAI_BRIDGE_PORT_ATTR_BRIDGE_PORT_NEXT_HOP_GROUP_ID for nexthop selection. Nexthop wll be the one of the available VTEP tunnels.

There can be an associated protection NHG configured SAI_BRIDGE_PORT_ATTR_BRIDGE_PORT_PROTECTION_NEXT_HOP_GROUP_ID, as a backup path in case the bridge port goes down.