app/testpmd: add 5-tuple swap forwarding engine

app/testpmd: add 5-tuple swap forwarding engine

The new 5-tuple swap engine swaps:
source and destination mac address,
source and destination address in ipv4/ipv6,
source and destination port in UDP/TCP.

The forwarding engine will parse each layer
and swap it, and will stop when the next
layer doesn't match.

The mentioned headers of ICMP/ARP/Multicast
packets will be swapped as well according to
matching layers.

usage: --forward-mode=5tswap

Signed-off-by: Shiri Kuzin <shirik@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>