[2.0] Replace Optional fields with Lists that accept a Union of options, ensure options have a valid name

[dbirman]

Describe the solution you'd like

• Core models with large numbers of Optional fields are replaced with List[Union[...]]
• AindModel gets a new name field
• AindModel children with an existing name field get removed
• Validators check that all data in these lists have a valid name (non-empty string)
• Write upgraders for all models that can take v1.X files and upgrade to 2.0

Describe alternatives you've considered
The name field disambiguates options without the need for a dictionary.

Additional context
https://alleninstitute.sharepoint.com/:w:/r/sites/NeuralDynamics/_layouts/15/Doc.aspx?sourcedoc=%7BE27B889D-27A1-4CC0-948C-10ADBE605654%7D&file=Data+Schema+2.0.docx&action=default&mobileredirect=true&DefaultItemOpen=1