Refactor method names to remove snake_case

[prohladenn]

pull request

This pull request primarily refactors the test method names to follow camelCase naming conventions, improving code readability and consistency. Additionally, it makes a minor documentation fix and updates a method name format check in the Checkstyle configuration.

Test code cleanup and consistency:

• Renamed all test methods from snake_case to camelCase to align with Java naming conventions.
• Updated the MethodNameCheck format in checkstyle.xml to require camelCase method names without underscores, enforcing the new convention.
• Fixed a relative link in CONTRIBUTING.md for the Gradle update instructions to use the correct path.

Issue: #3028

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[kahgoh]

Thanks for updating the tests and adding to the Checkstyle rule! Also thanks for fixing the link in CONTRIBUTING.md!