Better support for nested repos or linked repos

It is not uncommon for folks to have a single repo which contains multiple clojure "modules" or "packages" in subdirectories, each with their own deps.edn and tests.edn. Or to be working on multiple related projects at once by using :local/root in deps.edn.

Kaocha (in particular kaocha.runner and kaocha.repl) don't have a good story here, because they will only look for a tests.edn in the project's current working directory. You can point them to a different config file, but the (relative) paths provided in the tests.edn won't resolve to the intended paths.

Not sure yet how to best approach this, just leaving this here to be picked up and considered in the next development cycle.

I think the main mechanism that's needed is the ability to take multiple [test-config root-dir-path] pairs, and merge them into a single config, where source and tests paths have been adjusted accordingly.

Start by reading kaocha.runner and kaocha.repl, then trace how they locate tests.edn and resolve its relative source and test paths. Compare that behavior with the nested deps.edn and :local/root layouts described in the issue. Done should mean multiple test-config/root-dir pairs can be combined while preserving each module's intended paths.