Kernel/NetworkTask: Handle packets from "Closed" state

[Optimoos]

A TODO suggested that sending an RST may be desirable from the Closed state. This behaviour is defined in section 3.5.2 of the RFC, which this change implements.

Although there were no failures shown with initial testing, I'll note that this is difficult to validate as Closed sockets are typically cleaned up quickly.

RFC 9293: https://datatracker.ietf.org/doc/html/rfc9293

[timschumi]

Let's name this commit after what it really does, since it doesn't just clean up a TODO.

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs. Thank you for your contributions!

[stale[bot]]

This pull request has been closed because it has not had recent activity. Feel free to re-open if you wish to still contribute these changes. Thank you for your contributions!