selftests/net: packetdrill: add tcp_disorder_fin_in_FIN_WAIT.pkt

Commit 795a7dfbc3d9 ("net: tcp: accept old ack during closing")
was fixing an old bug, add a test to make sure we won't break
this case in future kernels.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Menglong Dong <menglong8.dong@gmail.com>
Link: https://patch.msgid.link/20260313115429.3365751-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>