Treat empty curly generic defaults in an extends clause in a .js file as any

[mhegazy]

When instantiating a generic base type in an extends clause, we allow generic type references to miss type parameters. for that we use the defaults if available (see #14907) then fill them with any.

React components now have generic defaults for props and state to be {}. this breaks the JS experience making all React components in a js file property-less. we should fall on the permissive side in a .js file, and special case {} to be treated as any.

Reported originally in #14558