Add a bpf_tcp_ca selftest for the TCP_NODELAY restriction in
bpf-tcp-cc.
Update bpf_cubic to exercise init() and cwnd_event_tx_start(),
and check that both callbacks reject bpf_setsockopt(TCP_NODELAY)
with -EOPNOTSUPP.
Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260421155804.135786-5-kafai.wan@linux.dev