This is a dummy target which calls clojure -X:test in the current
project. In multi-module projects, it runs through all configured
modules unless :exoscale.project/testable? is set to false in the
project file and calls clojure -X:test.
Note that it is still on each individual projects to set up the :test
alias correctly.
The default project templates wires kaocha as the runner for convenience.