Merge branch 'selftests-move-netfilter-tests-to-net'

Florian Westphal says:

====================
selftests: move netfilter tests to net

First patch in this series moves selftests/netfilter/
to selftests/net/netfilter/.

Passing this via net-next rather than nf-next for this reason.

Main motivation is that a lot of these scripts only work on my old
development VM, I hope that placing this in net/ will get these
tests to get run in more regular intervals (and tests get more robust).

Changes are:

- make use of existing 'setup_ns' and 'busywait' helpers
- fix shellcheck warnings
- add more SKIP checks to avoid failures
- get rid of netcat in favor of socat, too many test
  failures due to 'wrong' netcat flavor
- do not assume rp_filter sysctl is off

I have more patches that fix up the remaining test scripts,
but the series was too large to send them at once (34 patches).

After all scripts are fixed up, tests pass on both my Debian
and Fedora test machines.

MAINTAINERS is updated to reflect that future updates should be handled
via netfilter-devel@.
====================

Link: https://lore.kernel.org/r/20240411233624.8129-1-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>