Deleting a persisted object does not recursively delete all the descendants in the tree

[hi-liang]

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[hi-liang]

I'm starting to think we need a separate microservice to handle specifically cleanup, both for TTL and unbounded tasks like this. While we shouldn't have an issue with circular references as each iteration removes entries referencing the previously deleted ones, this shouldn't be a potential block for more regular tasks like updating persist objects on the main persist thread.

We also don't have anything that cleans up orphans. Ideally those should be ignored by clients but it's still debris that should be cleaned out