network/litep2p: Investigate low peer count for long-running node

[lexnv]

2 Kusama nodes were started on 23th April and left running.

{__name__="substrate_build_info", chain="ksmcc3", instance="localhost:9615", job="substrate_node", name="gray-vase-1131", version="1.10.0-1a45bd88348"}

The commit was based on a2a049db2bd, from branch:

• https://github.com/paritytech/polkadot-sdk/tree/lexnv/test-litep2p-latest

Both long-running nodes present a low peer count.

2024-07-02 11:34:18.796  INFO tokio-runtime-worker substrate: 💤 Idle (1 peers), best: #23863740 (0x8b9d…8738), finalized #23863736 (0x104a…6c67), ⬇ 1.4kiB/s ⬆ 2.9kiB/s    
2024-07-02 11:34:23.797  INFO tokio-runtime-worker substrate: 💤 Idle (1 peers), best: #23863740 (0x8b9d…8738), finalized #23863736 (0x104a…6c67), ⬇ 6 B/s ⬆ 6 B/s    
2024-07-02 11:34:28.797  INFO tokio-runtime-worker substrate: 💤 Idle (1 peers), best: #23863740 (0x8b9d…8738), finalized #23863736 (0x104a…6c67), ⬇ 1.0kiB/s ⬆ 1.4kiB/s    
2024-07-02 11:34:33.798  INFO tokio-runtime-worker substrate: 💤 Idle (1 peers), best: #23863740 (0x8b9d…8738), finalized #23863736 (0x104a…6c67), ⬇ 0 ⬆ 0   

[dmitry-markin]

What about inbound connections? Does the node have unreachable p2p port? 1 sync peer means that there are no inbound connections either.