Add regression test to check language specific rules are in *CheckList

When adding a language specific rule, one must add it in the <LANG>CheckList.java - remove the generic one and add a specific one to the list of checks to run.

This step can easily be forgotten, and even if there is a language specific implementation with working unit tests, there's no integration test to make sure it actually gets called at runtime by the plugin.

We should have on all plugins a regression test to make sure all Checks inside the plugin package are returned by the *CheckList.checks() method.

We've done a similar thing for the .NET integration tests - see EnsureAllTestsRunBase.java