chore/fix: use mirror repository for paper dev-bundles

[PierreSchwang]

Overview

Uses a custom nexus repository, which caches the dev-bundles. Should help with the occasional CI errors. The repository should only be able to serve dev-bundles.
Unused bundles (not used within the last 28 days) are deleted from the mirror. Otherwise, those are cached indefinitely. Listing for bundles is not possible - that's why renovate still needs to test against paper repo

Submitter Checklist

• Make sure you are opening from a topic branch (/feature/fix/docs/ branch (right side)) and not your main branch.
• Ensure that the pull request title represents the desired changelog entry.
• New public fields and methods are annotated with @since TODO.
• I read and followed the contribution guidelines.