The deleteRangeInBatches function is currently accepting as argument an executor and returning an ExecutorFuture. However, with the introduction of the range deleter service, the deletion will have to be called from within an executor.

Purpose of this ticket is to pull out the current code in a function deleteRangeInBatches, make it accept an OperationContext* and make it public. This way it can both be called by the legacy range deleter (via a new function deleteRangeInBatchesWithExecutor) and by the new range deleter service.