Add plugins snapshots repository

[michalvavrik]

Summary

When someone does mvn clean verify and doesn't have Quarkus QE Test Framework built locally already, compilation fails over missing artifacts (unless you have your settings configured for the snapshots). We already have the snapshots repository added here https://github.com/quarkus-qe/quarkus-test-suite/pull/2224/files so there is no point of not doing same for plugins (because the test preparer is a plugin).

Please select the relevant options.

• Bug fix (non-breaking change which fixes an issue)
• Dependency update
• Refactoring
• Backport
• New scenario (non-breaking change which adds functionality)
• This change requires a documentation update
• This change requires execution against OCP (use run tests phrase in comment)

Checklist:

• Methods and classes used in PR scenarios are meaningful
• Commits are well encapsulated and follow the best practices