Follow up for #14082

We probably want to start with our open source plugins where we basically want to ensure

• all changes from 3.x are merged into 4.x
• tests are running with the 4.x branch (not sure if that works already or whether it needs a beta?)
• ideally we have a green build for the 4.x branch of each plugin
• and maybe could also do some basic minimal functional test with each plugin with 4.x
• we check the version constraints are good in plugin.json (version = 4.0.0 and we require Matomo 4)
• once it’s all good we publish a new version for the plugin on the marketplace from the 4.x-dev branch by tagging it.