Prefix SID for BGP-LU

This feature introduces the BGP prefix segment ID (SID). A BGP prefix SID is always a global SID within the segment routing domain and identifies an instruction to forward the packet over the ECMP best path computed by BGP to the related prefix. The BGP prefix SID is the identifier of the BGP prefix segment. This feature also introduces a new BGP attribute, known as the BGP Prefix-SID attribute, and defines some rules to originate, receive, and handle error conditions for the attribute. The BGP Prefix-SID attribute can be attached to prefixes from Multiprotocol BGP IPv4/IPv6 Labeled Unicast.