selftests/net: packetdrill: cover RST validation in SYN-RECEIVED

selftests/net: packetdrill: cover RST validation in SYN-RECEIVED

Add packetdrill coverage for the RFC 9293 reset checks on request
sockets in SYN-RECEIVED.  Verify that an exact RST removes the request,
a non-exact in-window RST sends a challenge ACK without removing it,
and an out-of-window RST is silently discarded.

Also cover an RST|ACK with an unacceptable ACK number to ensure RST
sequence validation runs before ACK-field validation.

Signed-off-by: Yuxiang Yang <yangyx22@mails.tsinghua.edu.cn>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260717081443.809393-3-yangyx22@mails.tsinghua.edu.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>