Add handling author errors update for unnamed region and form landmarks?

[scottaohara]

region requires a name from authors, and form will require author naming.

If names are not provided, should we note in the Handling Author Errors section that these landmarks should not be exposed if authors fail to provide them?

HTML AAM already notes that if names are not provided, then section and form have no corresponding role (will be updated to role=generic).

[JAWS-test]

I'm for that. This consistency between ARIA and HTML makes sense to me. Core AAM should then be updated for form as well