Fix jruby support to handle messages nested more than 1 level deep

[rdubya]

This fixes #8191

[acozzette]

Thanks, @rdubya! I believe you will need to add the new test files here to fix the test failures.

[rdubya]

Hey @acozzette, sorry about missing that step again. I also updated the test structure to match the other ruby tests better.

[rdubya]

@acozzette are those failures something else I need to change? The details links don't give me any info.

[acozzette]

@rdubya Sorry about that, I can't see any details either. Let me rerun the tests and see if we get more informative results. If that doesn't fix it then there might be another problem because we have been having some issues with access to the test logs.