In 8.0, we will be deprecating movePrimary by turning it into a noop that logs a warning to use moveCollection to move data rather than movePrimary. The balancer will be updated to drain unsharded collections as well as sharded ones. But we will still need a ddl operation to commit the change of database primary at the end of the draining phase.

This ticket is to introduce a new command that will move only user system collections (which are untracked and so cannot be moved by the balancer) and then update the databasePrimary shard metadata.