Merge branch 'testing-make-netfilter-selftests-functional-in-vng-environment'

Merge branch 'testing-make-netfilter-selftests-functional-in-vng-environment'

Florian Westphal says:

====================
testing: make netfilter selftests functional in vng environment

This is the second batch of the netfilter selftest move.

Changes since v1:
- makefile and kernel config are updated to have all required features
- fix makefile with missing bits to make kselftest-install work
- test it via vng as per
   https://github.com/linux-netdev/nipa/wiki/How-to-run-netdev-selftests-CI-style
   (Thanks Jakub!)
- squash a few fixes, e.g. nft_queue.sh v1 had a race w. NFNETLINK_QUEUE=m
- add a settings file with 8m timeout, for nft_concat_range.sh sake.
  That script can be sped up a bit, I think, but its not contained in
  this batch yet.
- toss the first two bogus rebase artifacts (Matthieu Baerts)

scripts are moved to lib.sh infra. This allows to use busywait helper
and ditch various 'sleep 2' all over the place.

Tested on Fedora 39:

vng --build  --config tools/testing/selftests/net/netfilter/config
make -C tools/testing/selftests/ TARGETS=net/netfilter
vng -v --run . --user root --cpus 2 -- \
        make -C tools/testing/selftests TARGETS=net/netfilter run_tests

... all tests pass except nft_audit.sh which SKIPs due to nft version mismatch
(Fedora is on nft 1.0.7 which lacks reset keyword support).

Missing/WIP bits:
- speed up nf_concat_range.sh test
- extend flowtable selftest
- shellcheck fixups for remaining scripts
====================

Link: https://lore.kernel.org/r/20240418152744.15105-1-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>