refactor: replace lopg.ObserverLogs with logptest

[kruskall]

What does this PR do?

ObserverLogs is relying on a testing package in a non-test package

move to logptest

Why is it important?

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.md

Author's Checklist

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