Enable parallel tests

[koppor]

This PR enables parallel testing.

I learned about @ResourceLock - this helps much.

Aim: High CPU usage during tests

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Only Heisenbug - EntryComparatorTest fails in different entries:

Steps to test

Execute gradle task "check" in jablib

Mandatory checks

• [x] I own the copyright of the code submitted and I license it under the MIT license
• [x] I manually tested my changes in running JabRef (always required)
• [x] 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.