[Ci]code formatter

[spaceluke]

What's the purpose of this PR

See #5480

Brief changelog

1. add spotless code-style and header-license formatter plugin at pom.xml
2. apply the code formatter

Next step is append checker to CI-workflow

Follow this checklist to help us incorporate your contribution quickly and easily:

• Read the Contributing Guide before making this pull request.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit tests to verify the code.
• Run mvn clean test to make sure this pull request doesn't break anything.
• Update the CHANGES log.

[coderabbitai]

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[nobodyiam]

lgtm