Refactor tests to use parameterized tests

[Nakul-Shivaraj]

Refs JabRef#676
I am part of a Java graduate school class. My classmates will submit other PRs that address this issue as well.

This PR refactors multiple test classes to follow the one-assertion-per-test guideline and improve overall test readability and maintainability. Parameterized tests (@CsvSource) were introduced where appropriate to replace repetitive assertions.

Steps to test
To test this code run:

./gradlew :jablib:test \
--tests org.jabref.logic.layout.format.AuthorAndsReplacerTest \
--tests org.jabref.logic.layout.format.AuthorFirstLastOxfordCommasTest \
--tests org.jabref.logic.layout.format.AuthorLastFirstAbbrOxfordCommasTest \
--tests org.jabref.logic.layout.format.AuthorLastFirstAbbreviatorTest \
--tests org.jabref.logic.layout.format.RemoveBracketsTest \
--tests org.jabref.logic.layout.format.RemoveLatexCommandsFormatterTest

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)
• [/] I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• 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>.

[github-actions]

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[jabref-machine]

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