authority-discovery: Set intervals to start when authority keys changes (#3764)

The authority-discovery mechanism has implemented a few exponential
timers for:
- publishing the authority records
- goes from 2 seconds (when freshly booted) to 1 hour if the node is
long-running
  - set to 1 hour after successfully publishing the authority record
- discovering other authority records
- goes from 2 seconds (when freshly booted) to 10 minutes if the node is
long-running

This PR resets the exponential publishing and discovery interval to
defaults ensuring that long-running nodes:
- will retry publishing the authority records as aggressively as freshly
booted nodes
- Currently, if a long-running node fails to publish the DHT record when
the keys change (ie DhtEvent::ValuePutFailed), it will only retry after
1 hour
- will rediscover other authorities faster (since there is a chance that
other authority keys changed)

The subp2p-explorer has difficulties discovering the authorities when
the authority set changes in the first few hours. This might be entirely
due to the recursive nature of the DHT and the needed time to propagate
the records. However, there is a small chance that the authority
publishing failed and is only retried in 1h.

Let me know if this makes sense 🙏

 

cc @paritytech/networking

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Signed-off-by: Alexandru Vasile <[email protected]>
Co-authored-by: Dmitry Markin <[email protected]>