Add a test for verifying JPMS module info declarations (need new sub-module to run only on JDK 11+?)

[cowtowncoder]

One weak spot we have had for a long time now is that of goodness (or lack thereof) of our JPMS module-info.class definitions: they are created using Moditect, built on Java 8, and cannot do much in way of validation.

But it should be possible to create integration tests that do verify basic goodness of module info.

This may require splitting of tests into sub-modules, if we still want Java 8 tests run for other things.
Or potentially we could simply drop Java 8 support for this test module; either way would work.

Note: a follow-up thing to consider would be OSGi bundle loading testing in similar way.