Enriched representation of assays via subclass relationships

[anngvu]

This old csv was going to define additional relationships between assay classes, which is especially useful for new assays, but this was largely forgotten after migrating to LinkML (since this has always been an add-on component, and how exactly to translate to LinkML needed to be specified later).

Currently, assays are enums when they should be classes. To achieve a richer representation in the LinkML model, we will need to refactor and then implement https://linkml.io/linkml/schemas/enums.html#dynamic-enums with our own tooling (retold) for schema compilation to JSON-LD as described in https://linkml.io/linkml/schemas/enums.html#tooling-to-support-dynamic-enums:

Different tool chains may choose to implement dynamic enums differently.

For example, if you have a stack that uses JSON-Schema for validation, then tools may choose to materialize a dynamic query into a static list of terms at the time of schema compilation.

(So this is also blocked by updates to tooling first.)