Re: CALCITE-2458 Use of Kotlin for unit tests

[Vladimir Sitnikov]

Thanks everybody for your comments.

I've received no strong objections so far, so I assume lazy consensus.
I've merged the PR in
https://git-wip-us.apache.org/repos/asf?p=calcite.git;a=commit;h=55d86646fe598d215bd53dbeac2bbbf32a9506f9

Vladimir