Add vavr dependency to benchmarks pom.xml

[jon-wei]

This PR adds an undeclared io.vavr dependency to the benchmarks pom.xml, which was referenced in the changes from #11257

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[jon-wei]

Closing in favor of #11522