keepalive: trace in case of success

[muzarski]

cpp-rust-driver tests sometimes depend on logs emitted by the driver. HeartbeatTests are on of them. Tests look for a following log: logger_.add_critera("Heartbeat completed on host " + ccm_->get_ip_prefix());.

Before this commit, rust-driver was not emitting any logs in case of keepalive request success. I think it's not a bad idea to add a trace log here, considering that keepalive intervals are rather long (default is 30s).

Obviously, the logger criteria will need to
be adjusted in cpp-rust-driver tests as well.

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• [ ] I added relevant tests for new features and bug fixes.
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• PR description sums up the changes and reasons why they should be introduced.
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• [ ] I have adjusted the documentation in ./docs/source/.
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[Lorak-mmk]

Its a shame that there aren't more levels of logs. We could put this one in even lower level than trace.

[github-actions]

cargo semver-checks found no API-breaking changes in this PR! 🎉🥳
Checked commit: 3a0ca2e

[muzarski]

Its a shame that there aren't more levels of logs. We could put this one in even lower level than trace.

Maybe there is some mechanism in tracing that would allow us to define some custom CCP_RUST_DRIVER_LOG_LEVEL or something similar. But this would need investigation if something like this exists.

[muzarski]

Failed to apply group 0 change due to concurrent modification for retries::speculative_execution_panic_regression_test ...