Simplify error messages against intersections of weak types

I spoke a bit with @sandersn about ways we can tackle the type madness issue (#14662). I noted that JSX scenarios are much more broadly applicable right now and are pretty prevalent given the sorts of type arithmetic we see a lot of in the React community. :smiley: # Problem: JSX optional attributes make errors too hard to read ```tsx interface FooProps { name: string; age: number; } class Foo extends React.Component<FooProps> { constructor(props: FooProps) { super(props) } render() { const {name, age} = this.props; return <div>I'm {name} and am {age} years old</div>; } } // Type '{ blah: number; }' is not assignable to type 'IntrinsicAttributes & IntrinsicClassAttributes<Foo> & Readonly<{ children?: ReactNode; }> & Reado...'. // Type '{ blah: number; }' is not assignable to type 'Readonly<FooProps>'. // Property 'name' is missing in type '{ blah: number; }'. <Foo blah={10} />; ``` # Proposal When doing relation checks against an intersection target, if a check fails, see if relating against the same type with weak types removed would result in the same outcome. If so, use *that* comparison when elaborating types. The great part is that this actually solves a broader set of problems than just JSX.