selftests/bpf: Add push/pop checking for msg_verify_data in test_sockmap

selftests/bpf: Add push/pop checking for msg_verify_data in test_sockmap

Add push/pop checking for msg_verify_data in test_sockmap, except for
pop/push with cork tests, in these tests the logic will be different.
1. With corking, pop/push might not be invoked in each sendmsg, it makes
the layout of the received data difficult
2. It makes it hard to calculate the total_bytes in the recvmsg
Temporarily skip the data integrity test for these cases now, added a TODO

Fixes: ee9b352ce465 ("selftests/bpf: Fix msg_verify_data in test_sockmap")
Signed-off-by: Zijian Zhang <zijianzhang@bytedance.com>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20241106222520.527076-5-zijianzhang@bytedance.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>