Reformulate group tags tutorial

From @bernt-matthias in https://github.com/galaxyproject/training-material/pull/2512#discussion_r620973885

> Maybe it would be good to reformulate the tutorial such that the upload, apply rules, build collection paths are covered. The only difference seems to be that the URL column needs to (can be) be defined only in the upload option.

Start with the tutorial discussed in pull request #2512 and review how it currently presents upload, applying rules, and building collection paths. Reformulate the tutorial to cover those workflows, including that the URL column can be defined only in the upload option; done means the tutorial clearly explains these steps and their difference.

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