RFC: Consider using an actual Wren testing library

[joshgoebel]

The existing Python based testing is needlessly frustrating for simple Wren based logic testing, example:

https://github.com/joshgoebel/wren-console/blob/d1d8df30e9dc6f9844caf00a676a4ed944efa89e/test/io/file/basename.wren

There is no need for the entire output/redirection/verification process here. This could all be done 100% inside Wren with simple equality checking, etc... ie any of the existing Wren testing suites could be used. This also allows for MUCH nicer errors in cases of test failures.

My own wren-console project goes ahead and adds wren-testie for some of our newer functionality [regarding writing much more of the CLI in pure-Wren] (which I'm not sure will ever be upstreamed)... but now we'd also like to be able to use the simpler unit testing for some things that may get upstreamed (dirname, basename, etc), hence this issue being opened.

I of course naturally prefer wren-testie - and it would give me a good reason to ensure it continues to remain functional on both CLI and Console in the future, but really any nice Wren testing framework would be an improvement I think.

Thoughts?