selftest: packetdrill: add tcp_timestamping_tcp_tx_timestamp_bug.pkt

selftest: packetdrill: add tcp_timestamping_tcp_tx_timestamp_bug.pkt

Test tcp_tx_timestamp() behavior after ("tcp: tcp_tx_timestamp()
must look at the rtx queue").

Without the fix, this new test fails like this:

tcp_timestamping_tcp_tx_timestamp_bug.pkt:55: runtime error in recvmsg call: Expected result 0 but got -1 with errno 11 (Resource temporarily unavailable)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://patch.msgid.link/20260127123828.4098577-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>