Improve Args API for non-optional fields for TypeScript users

[donaldpipowitch]

Is your feature request related to a problem? Please describe
I recently used the Args API with non-optional fields and this led to some problems. I'm also not sure if this pattern is supported or not. The full background with code examples can be found here.

Describe the solution you'd like

1. Clarify if non-optional fields in the Args API are allowed or not.
2. If non-optional fields are allowed the Partial<> on args should IMHO be removed.
3. If non-optional fields are not allowed such a usage should be forbidden or raise warnings. (Maybe this can be raised on the type level already - basically disallowing fields which don't allow undefined - or one could start creating officially baked Storybook ESLint rules - I don't think they already exist or?)

Describe alternatives you've considered
The solution contains alternatives.

Are you able to assist to bring the feature to reality?
Yes.

Additional context

[shilman]

closing as duplicate to #13747