This allows the type's return value to be accessed more easily.
Motivating use case:
- Built-in module provides CLI functionality by declaring
an `attrListWith { asAttrs = true; }`, extracting the ordered list
from `valueMeta` for the purpose of creating the `argv`.
- User modules can read the command line's flags directly without
having to parse the list of attrs.
This adds a type for name-value mappings that preserve ordering.
Motivating use case: command line flags for package modules /
wrappers / modular services.
The option value can be transformed into a command line in the
correct order.
Additionally, a convenience readOnly option could be provided
to give easy introspection access to the values in an ad hoc
manner.
Robert Hensing