Dev: Organize tests by namespace

[rads]

Right now the bb tests task is hard-coded to run tests.clj.

To keep the test suite manageable going forward it would be helpful if we could support the standard clojure.test conventions with a test directory containing a _test.clj file for each namespace.

I think we could work around this temporarily by manually requiring more test namespaces inside this file, but it's not ideal.

[borkdude]

Agreed