code: Allow applications to dynamically adjust log level whenever consensus goes to round 1+

[romac]

No description provided.

[adizere]

The requirement seems to be:

• if round > 0, then node operators should be able to witness more observable/verbose logs

Probably there are other situations where this is relevant, eg upon rejecting a proposal or upon various timeouts. But let's focus on the round > 0 case first.

I wonder if there's simpler ways to achieve this without dynamically adjusting log levels, eg having a span that wraps the code that handles round > 0 logic, ensuring that logs within that span have differentiated logging treatment?

[romac]

We already log some messages as warnings when a timeout occurs and we move to round > 0.

But the idea was to get all subsequent logs at debug or info level, and for this we need to change the log level dynamically, which is totally supported by tracing-subscriber. We just need a way to let the application know that it should so, since it is the app and not consensus which installs the subscriber that manages the log level.

[romac]

I just realized that consensus already sends a HostMsg::StartedRound(height, round, proposer) message to the host whenever we move to a new round, so for this case, it would only be a matter of changing the log level whenever round > 0.