Provide raw data in non-reactive form as part of afmm

[ml-ebs-ext]

According to the "Arguments from Module Manager" vignette, afmm provides, among others: unfiltered_dataset and filtered_dataset. Those are only resolvable in reactive time.
Some modules could benefit from being able to inspect the full suite of datasets provided to the application at start time. That would allow them to:

• Detect app creation mistakes.
• Pre-compute UIs for all possible dataset selection.
• ...

The proposal is to introduce a new afmm member offering that information. Maybe it could be named just "data" and be mostly a pass-through of the dv.manager::run_app() data argument. "Mostly" because run_app allows to provide functions instead of datasets and those would need to be evaluated first.