Feature Request: native unit testing support

Some users can not use https://github.com/gpestana/kapacitor-unit due to it's dependency on Docker.

Start by reviewing the issue and the linked kapacitor-unit project to understand which Docker dependency prevents native unit testing. Define the native testing scope and confirm that the resulting support works without Docker; the payload names no repository files or existing tests to run.

Written by the indexing model from the issue text.