Migrate to mailman 3

Mailman3 configured in !437 (merged).

• Enable VERP for lists: https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/mta/docs/verp.html
• VERP probes: https://docs.mailman3.org/projects/mailman/en/latest/src/mailman/config/docs/config.html#verp-probes
• listowners@archlinux.org 🤔

Migrated lists:

• arch-announce (!437 (merged))
• arch-commits (4d8dfb6a)
• arch-dev (bb000824)
• arch-devops (bb000824)
• arch-devops-private (!437 (merged))
• arch-dev-public (bb000824)
• arch-events (!437 (merged))
• arch-general (75ac7d09)
• arch-magazine
• arch-mirrors (bb000824)
• arch-mirrors-announce (bb000824)
• arch-multilib (bb000824)
• arch-notifications
• arch-ports (bb000824)
• arch-proaudio (bb000824)
• arch-projects (bb000824)
• arch-releng (bb000824)
• arch-security (4d8dfb6a)
• arch-test (test mailing list, not worth migrating)
• arch-tu (bb000824)
• arch-wiki-admins (!437 (merged))
• arch-women (bb000824)
• aur-dev (4d8dfb6a)
• aur-general (75ac7d09)
• aur-requests (75ac7d09)
• mailman
• pacman-contrib (4d8dfb6a)
• pacman-dev (4d8dfb6a)
• staff (bb000824)

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Migrate and ansible our current mailman setup to mailman 3. A wip branch is available in our git repository.