Eliminate the manual process of creating CI tests

[khajavi]

We need to use the following setting keys to perform CI tests: ciTargetJavaVersions, ciTargetMinJavaVersions, and ciTargetScalaVersions.

However, these are implementation details and we should not expect the user to fulfill these settings. Instead, we should read all submodules and identify which projects are to be tested (test/skip := true). Then, we can read the crossScalaVersions and javaPlatform setting keys to generate CI tests automatically, without any manual intervention.