Uses JVM agent for Mockito

[alecharp]

Description

This to resolve a warning in Maven build log since Java 21.
Mockito core must be attached as a JVM agent.
Following https://javadoc.io/doc/org.mockito/mockito-core/latest/org.mockito/org/mockito/Mockito.html#0.3.

Testing done

Ran mvn verify locally and saw the warnings disappear.

Submitter checklist

• If an issue exists, it is well described and linked in the description
• The description of this pull request is detailed and explain why this pull request is needed
• The changeset is on a specific branch. Using feature/ for new feature, or improvements ; Using fix/ for bug fixes ; Using docs/ for any documentation changes.
• If required, the documentation has been updated
• There is automated tests to cover the code change / addition or an explanation why there is no tests in the description.