Enhance tcpstat collector

Good day,

I would like to propose an extension of the tcpstat collector by adding metrics for specific ports for local or remote. Now it is only possible to display only the total list of all connections.

I don't know if someone here had a similar idea, but I didn't find any issues on this topic and I could pass this to our programmers, if this idea was accepted.

In my opinion, 2 new parameters could be added with lists as a parameter:
--collector.tcpstat.port.local=["80","443"]
--collector.tcpstat.port.remote=["443"]

This would create metrics such as:
node_tcp_connection_states_port{state="...", port="...", type="(local|remote)"}

If you have any suggestions how to do this differently please let me know.

Start by reading the tcpstat collector entry point and how its existing connection-state metrics are assembled. Determine how local and remote port lists should be configured, then verify that the collector exposes port-labeled metrics for the requested states and connection direction.