[docs] Set pattern for storybook controls vs stories

[werdnanoslen]

Does this documentation relate to a specific USWDS feature?
No, relates to our general storybook use

Is your documentation related to a problem or inconsistency? Please describe.
Inconsistency in using and creating stories

Describe the documentation you'd like
Let's set a pattern for using storybook controls vs stories. What component features should/can be set by storybook controls, and when do we split into separate stories. Once we have a solid pattern, let's roll that out to all components for a consistent experience.

Additional context

• A good example may be the text-input component, where many of these stories' differences could instead be set by controls, allowing for a better experience in experimenting with how such an input may render
• There've been some significant improvements in controls, which would require an update to our Storybook package (see feat(storybook): storybook 7 #2533)