Peer health checks

[shubham3121]

Description

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Affected Dependencies

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• track ping status, ping message and ping timestamp at NodePeer level
• add a utility track peer route healthcheck
• add a network service to find peer
• add an integration test for peers health check

How has this been tested?

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Checklist

• [ ] I have followed the Contribution Guidelines and Code of Conduct
• [ ] I have commented my code following the OpenMined Styleguide
• [ ] I have labeled this PR with the relevant Type labels
• [ ] My changes are covered by tests

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[khoaguin]

TODO in this PR:

• Integrate background_tasks in orchestra

2. for run_peer_health_checks background task

• What is the ping status of a peer if association request is submitted but not accepted?
• What is the ping status if the association request is accepted?
• If one peer node goes down, what is the ping status (may not be checked with a Python Node. Try starting a server with HTTP connection)
• what is the ping status when a peer is deleted -> create remote client on that node peer -> check peer list -> peer not found

3. Since we can get domain health status now with the new peers health check functionalities, we can just grab the online domains from the database and no longer need to check it like currently in DomainRegistry.online_domains using a ThreadPoolExecutor

[shubham3121]

Great work @khoaguin and @kiendang !!! Left a few minor comments.