tests: 30s-stress: add failslab and abort phase tests

tests: 30s-stress: add failslab and abort phase tests

Pablo suggested to also cover abort phase by intentionally deleting
non-existent or adding clashing keys.

While at it:
add rules with anon sets and jumps to anonymous chains and a few
constant sets.

Pick different key sizes so there is a higher chance kernel picks
different backend storages such as bitmap or hash_fast.

add failslab support, this also covers unlikely or "impossible" cases like
failing GFP_KERNEL allocations.

randomly spawn 'nft monitor' in the background for a random duration
to cover notification path.

Try to randomly delete a set or chain from control plane.

Randomly set a table as dormant (and back to normal).

Allow to pass the test runtime as argument, so one can now do

./30s-stress 3600

to have the test run for one hour.

For such long test durations, make sure the ruleset
gets regenerated periodically.

Signed-off-by: Florian Westphal <fw@strlen.de>