Always show and explain how collections / multiple="true" data inputs are processed #20657
Description
We currently have a nice documentation for data inputs with multiple="false" when users input a collection (or just multiple manually selected datasets), i.e. it's shown explicitly that the data is processed in batch and what exactly this means. But Xref #19234
Even if there are just the two cases (bulk/batch) users seem to struggle a lot with realizing which is the case (often just following assumptions
what the tool should do, e.g. here).
We should also document and explain for the case when we do bulk processing, of input collections (or multiple manually selected datasets). The docs would fit much better in Galaxy itself than, e.g. GTN (a tutorial over there might still be good). Also documenting how a tool that does implement bulk processing can still be used to batch process data would fit there nicely. In this context I was also thinking if we should add a User documentation category to https://docs.galaxyproject.org/?
Maybe a new collection tool would be also good that simplifies nesting a collection for batch process data with a tool that implements bulk processing.