selftests: mptcp: test last time mptcp_info

This patch adds a new helper chk_msk_info() to show the counters in
mptcp_info of the given info, and check that the timestamps move
forward. Use it to show newly added last_data_sent, last_data_recv
and last_ack_recv in mptcp_info in chk_last_time_info().

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240410-upstream-net-next-20240405-mptcp-last-time-info-v2-2-f95bd6b33e51@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>