List available reporters and validate selected reporters

[Deraen]

I couldn't find list of built-in reporters in the documentation and had to look at the source code. Reporter option docs should list the built-in reporters, and even better would be to provide --list-reporters option so the choices can be listed from CLI.

Also, some kind of validation for :reporters would be useful. E.g. kaocha.report.progress/progress seems to work mostly, but doesn't print failures. The correct value is kaocha.report.progress/report. (Or just ensure there aren't public vars that might be accidentally used in report namespaces).

[plexus]

Reporters are documented here: https://cljdoc.org/d/lambdaisland/kaocha/0.0-413/doc/3-configuration#reporters

If that list is incomplete or inaccurate then a PR would very much be appreciated.

--list-reporters seems like it would be useful, but not sure how it would work, since reporters are just functions. e.g. how would we find reporters provided by third parties?

[Deraen]

Would be helpful if --list-reporters listed just the built-in reporters.

The docs currently list some reporters which include result reporter, like dots and documentation and then progress which doesn't include result. And the reporter docs don't mention this result reporter.

[alysbrooks]

I remember experimenting with an approach of using metadata to tag functions as reporters. I still like that idea, but I suspect it isn't a particularly high priority.