selftests: netfilter: update makefiles and kernel config

selftests: netfilter: update makefiles and kernel config

Jakub reports the Makefile missed a few updates to make kselftest-install
work for the netfilter tests and points out that config file lacks many
dependencies such as VETH support.

The settings file (timeout 8m) is added for nft_concat_range.sh script
which can take several minutes to complete.

Fixes: 3f189349e52a ("selftests: netfilter: move to net subdir")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Closes: https://lore.kernel.org/all/20240412175413.04e5e616@kernel.org/
Signed-off-by: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/r/20240418152744.15105-13-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>