selftests/net: packetdrill: run in netns and expand config

Run packetdrill tests inside netns.
They may change system settings, such as sysctl.

Also expand config with a few more needed CONFIGs.

Link: https://lore.kernel.org/netdev/20240910152640.429920be@kernel.org/


Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240912005317.1253001-2-willemdebruijn.kernel@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>