Clean up nodes, databases, manifests

Once the migration is done and no regression is detected [1], clean up the leftovers:

• databases (belvedere, bardo, ...)
• puppet manifests with no longer required db instructions...
• intermediary dumps used to shuffle data around

Some of those may already be done. Just make sure the rest is cleaned up as well.

• [1] #3833 (closed)

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Migrated from T3849 (view on Phabricator)