Add Fullnode network port diagnostic mechanism

[mvines]

Problem

I burned a ton of time in #3840 debugging what ultimately turned out to be an incorrect inbound network configuration of the VM I was using. Repair requests from other nodes were being blocked by the firewall settings 🤕. This is very likely going to be a problem for others and we'll surely have a ton of support requests as a result.

Proposed Solution

Add a mechanism solana-fullnode,solana-gossip, or some other cli tool that ensures that all inbound/outbound ports are not being blocked, perhaps via some ping/pong with the cluster entry point node.

Also confirm that the ports reported over gossip by other nodes are accessible.