Starting from v6.2 (SERVER-69768), range deletion documents created in config.rangeDeletions contain a shard key pattern field. This means that only range deletions created before v6.2 may potentially be still present on disk without a shard key pattern field set.

Purpose of this ticket is to implement an upgrade procedure to populate "outdated" range deletion task documents with the key pattern when upgrading to v9.0. This is a necessary step to get rid of the shard key pattern retrieval code starting from v9.1, last mile to totally detach the range deleter from sharding machinery.

It will not be necessary to delete the field on downgrade as keeping it doesn't harm.