selftests/bpf: Add tests for bucket resume logic in established sockets

Replicate the set of test cases used for UDP socket iterators to test
similar scenarios for TCP established sockets.

Signed-off-by: Jordan Rife <jordan@jrife.io>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>