Fix severity level of gzlog

[azeey]

🦟 Bug fix

Fixes #632

Summary

The severity level of gzlog was incorrectly set to err. Changing this to trace solves two problems:

1. The log message is now a lot less alarming
2. When running gz sim -v4, this message is not shown on the console. It will only be logged to file. It does show up on the console if you run with -v5.

The second point is technically a behavior change since in Harmonic, regardless of the verbosity level, gzlog would never show up on the console. However, duplicating that behavior with the new Console implementation proved to be very complicated. So, I propose we change the meaning of gzlog to be equivalent to gztrace.

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Note
We'll have to make new prereleases of all downstream libraries for this fix to propagate. I vote we just wait for the stable release.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[iche033]

The test failures look related, probably due to behavior change?