Added PersonNamesPlausibilityComparator to improve merge dialog selection for author fields

[D-Prasanth-Kumar]

Closes #14454

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
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• I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.

Screenshot: Merge dialog selecting correct DOI author data

[koppor]

Sure that one of it can be null?

I bet that both are non-null - and you can annotate the whole class as @Nullmarked (because nothing is null)

[koppor]

No vars in JabRef code.

[koppor]

If possible, please add test cases, too.