Replaced Utils.join() with JDK API.

[samalapurapu]

Problem

Solution

Does this solution apply anywhere else?

• yes
• no

If yes, where?

Test Strategy

Testing done:

• Unit tests
• Integration tests
• System tests
• Manual tests

Release Plan

[confluent-cla-assistant]

🎉 All Contributor License Agreements have been signed. Ready to merge.
_{Please push an empty commit if you would like to re-run the checks to verify CLA status for all contributors.}

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[vbalani002]

Thanks @samalapurapu ! Can we backport this change to the oldest supported feature branch please?

[sappusaketh]

@samalapurapu or @vbalani002 can this be merged? This is blocking us from upgrading to kafka 3.8+