Fixes bugs in divide_recipe() to avoid unnecessary duplication of variables and ensure that the 'Datasets' section of the atomic recipe has the correct structure

When trying to split a recipe, if the elements to be split (Variable, Dataset, etc) were not inside a list, the splitting was not performed correctly, causing duplicated atomic recipes, and atomic recipes with wrong formatting that resulted in errors during the workflow.

The changes in divide_recipe() fix this by detecting if the elements is not a list and transforming it to one prior to splitting.