This code was taken from VPP's src/plugins/linux-cp/ directory, originally by:
Signed-off-by: Neale Ranns <nranns@cisco.com>
Signed-off-by: Matthew Smith <mgsmith@netgate.com>
Signed-off-by: Jon Loeliger <jdl@netgate.com>
Signed-off-by: Pim van Pelt <pim@ipng.nl>
Signed-off-by: Neale Ranns <neale@graphiant.com>

See previous work:
https://gerrit.fd.io/r/c/vpp/+/30759 (interface mirroring)
https://gerrit.fd.io/r/c/vpp/+/31122 (netlink listener)

It's intended to be re-submitted for review as a cleanup/rewrite of the existing
Linux CP interface mirror and netlink syncer.