selftests/bpf: Update tests for new ct zone opts for nf_conntrack kfuncs

Add test for allocating and looking up ct entry in a
non-default ct zone with kfuncs bpf_{xdp,skb}_ct_alloc
and bpf_{xdp,skb}_ct_lookup.

Add negative tests for looking up ct entry in a different
ct zone to where it was allocated and with a different
direction.

Update reserved test for old struct definition to test for
ct_zone_id being set when opts size isn't NF_BPF_CT_OPTS_SZ (16).

Signed-off-by: Brad Cowie <brad@faucet.nz>
Link: https://lore.kernel.org/r/20240522050712.732558-2-brad@faucet.nz


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>