Document Controlled vs Uncontrolled Component Design pattern

pursuant to this discussion https://twitter.com/dan_abramov/status/1001943857096003584

all react components can be:

• controlled (no internal state)
• uncontrolled (internal state)
• mixed (uncontrolled by default, unless some props are passed to make it controlled)

the current docs on controlled vs uncontrolled: https://reactjs.org/docs/uncontrolled-components.html focus entirely on forms, but this design pattern applies to -all- components. we should document this.

questions

1. What else should we say in the docs?
2. do we want to tell people that they can do "mixed control" or do we leave that for people to discover for themselves?
3. is this the same page as https://reactjs.org/docs/uncontrolled-components.html or is it a separate page?

Start with the existing uncontrolled-components.html documentation and the linked discussion. Resolve whether controlled, uncontrolled, and mixed component patterns belong on that page or a separate page, and determine the guidance the documentation should provide. Done means the selected documentation clearly covers the pattern beyond forms and answers the open scope questions.