"Absorb"/migrate already defined in BIDS dataset_description.json GeneratedBy

[yarikoptic]

It's definition presented in

• https://bids-specification.readthedocs.io/en/stable/glossary.html#generatedby-metadata

and it is specification / application described in

• https://bids-specification.readthedocs.io/en/stable/modality-agnostic-files.html#derived-dataset-and-pipeline-description

I proposed to adopt it more wider within BIDS:

• Allow for GeneratedBy in any sidecar .json file to collect their provenance bids-specification#1970
  which lead to triggering back attention to BEP028.

I think it would be quite important to "harmonize" that field with BEP028 proposed PROV to avoid confusion etc.

• At the very least there should be mapping (tool) to convert that record into proper PROV jsonld record
  • if not possible: clearly describe what is missing... may be could still be addressed
• Ideally IMHO we should
  1. establish generic JSON sidecar PROV record support (JSON and BIDS-Prov #146) and then
  2. provide automated migration for that GeneratedBy into that new sidecar field
     • relates: Provide "migrate" helper to adopt (new) standardized aspects in datasets bids-specification#1984
  3. announce "old" GeneratedBy (if stays the same name -- detect via schema) deprecated and later (2.0?) remove