Render valid value restrictions in tables based on object definitions in schema

[tsalo]

It would be great if tables in the specification automatically included restrictions on valid values, without having to hardcode those restrictions in the object "description" fields.

This stems from #827 (comment).

As a simple example, we can look at the CASLType metadata field:

bids-specification/src/schema/objects/metadata.yaml

Lines 299 to 307 in 251f440

	CASLType:
	name: CASLType
	description: |
	Describes if a separate coil is used for labeling:
	`"single-coil"` or `"double-coil"`.
	type: string
	enum:
	- single-coil
	- double-coil

Note that there are currently two valid values for this field: "single-coil" and "double-coil". These values are written out in two places: (1) the "enum" that actually restricts valid values for the field and (2) the "description", which redundantly includes the values. Optimally, we wouldn't need to include a list of valid values in the description, since that information is already available, in a more useful form, elsewhere in the object definition. One step in this direction is to update our table-rendering functions to attempt to convert restrictions on valid values to a human-readable form and append that new string to the "description" cell in the table automatically.

NOTE: Preferably, any enhancements to the code to implement this would also work with #904.