1) identify testcases which the usual pattern

• base class + two subclasses (one for jetty, one for tomcat) which only add a container-specific descriptor file
• replace these with a single test class and use AuxiliaryArchiveProcessor to append container-specific descriptors

2) for the rest of the cases either keep the current layout or move them to a single place and use categories/exclusions to keep the current behavior

3) Use the latest available container versions by default (add others in the CI job)