selftests: drv-net: Add ntuple (NFC) flow steering test

selftests: drv-net: Add ntuple (NFC) flow steering test

Add a test for ethtool NFC (ntuple) flow steering rules. The test
creates an ntuple rule matching on various flow fields and verifies
that traffic is steered to the correct queue.

The test forces all traffic to queue 0 via the indirection table,
then installs an ntuple rule to steer select traffic to a specific
queue. The test then verifies the expected number of packets is received
on the queue.

This test has variants for TCP/UDP over IPv4/IPv6, with rules matching
the source IP. Additional match fields will be added in the next commit.

 TAP version 13
 1..4
 ok 1 ntuple.queue.tcp4.src_ip
 ok 2 ntuple.queue.udp4.src_ip
 ok 3 ntuple.queue.tcp6.src_ip
 ok 4 ntuple.queue.udp6.src_ip
 # Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Dimitri Daskalakis <daskald@meta.com>
Link: https://patch.msgid.link/20260407164954.2977820-2-dimitri.daskalakis1@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>