[backport 11.0] update demo project artifact names so they don't interfere with l10n scanning

The demo project does not load the correct l10n bundles as the demo project artifacts use the same name prefix as currently used in the release pom. As there is just a single released artifact, and as that artifact has the same prefix as the demo artifacts, update the demo artifact names from <plugin>-demo to demo-<plugin> or similar.