Tool to run tests of multiple repos locally

@raphinesse built some nice automation (or used the appropriate tools) for https://github.com/raphinesse/cordova-cross-spawn-test
I think it would be a great idea to expand that into a `cordova-all-the-tests` repo (maybe with a more appropriate name) that we can clone and use to run all test suites locally.
Something like "manual CI" for all (platform, tooling, plugin) repos on our environments.

Functionality:
- Set up and prepare repositories
- Run all tests ("all" being configurable in a file)
- Run "sets" of tests: tooling, platforms, cli

This has partial overlap with `cordova-coho`, so we should check if there is some synergy or not.