tc: Introduce tc ct action

tc: Introduce tc ct action

New tc action to send packets to conntrack module, commit
them, and set a zone, labels, mark, and nat on the connection.

It can also clear the packet's conntrack state by using clear.

Usage:
   ct clear
   ct commit [force] [zone] [mark] [label] [nat]
   ct [nat] [zone]

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Yossi Kuperman <yossiku@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>