bgpd: evpn pip data struct and cli

bgpd: evpn pip data struct and cli

Evpn Primary IP advertisement feature uses
individual system IP and system MAC for prefix (type-5)
and self type-2 routes.

The PIP knob is enabled by default for bgp vrf instance.

Configuration CLI for enable/disable PIP feature knob.
User can configure PIP system IP and MAC to retain as
permanent values.

For the PIP IP, the default behavior is to accept bgp default
instance's router-id. When the default instance router-id change,
reflect PIP IP assignment.

Reflect type-5 to use system-IP and system MAC as nexthop and RMAC
values.

Ticket:CM-26190

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>