bgpd: Expand 'bgp default <afi>-<safi>' cmds

bgpd: Expand 'bgp default <afi>-<safi>' cmds

Adds new commands to allow a user to default 'default' address-families
to be inherited by all new peers.  Previously this was limited to just
ipv4/ipv6 unicast, now the full list is:
---
ipv4-unicast
ipv4-multicast
ipv4-vpn
ipv4-labeled-unicast
ipv4-flowspec
ipv6-unicast
ipv6-multicast
ipv6-vpn
ipv6-labeled-unicast
ipv6-flowspec
l2vpn-evpn
---

Signed-off-by: Trey Aspelund <taspelund@nvidia.com>