Deployment-prep has a etcd cluster but it's rather barebones and not widely used like its in production. To reduce amount of breakage from Puppet manifests expecting conftool and to reduce beta-production differences (T87220), could we set it up properly on beta?

The use cases I have in mind are properly fixing T277206, LVS backends (T196662: Set up LVS in beta like prod) and database management (currently maintenance like T277070 requires someone with mediawiki deployment access and takes ages to sync across the cluster), but those likely aren't the only places where this would be useful

Checklist

This is likely incomplete, feel free to add missing items

• Service records for etcd
  • Majavah created SRV records under svc.deployment-prep.eqiad1.wikimedia.cloud for etcd-server-ssl, etcd, etcd.conftool.
  • Not used yet, since SSL certificates do not match, WIP
• Conftool data/schema
  • production has this in ops/puppet, where to put these?
• Install tooling on deployment-cumin?
• Use for mw databases
• Write documentation