Ensure render_model always recieve a React.element

[davesnx]

No description provided.

[pedrobslisboa]

I disagree that render_model should always receive a React.element.
To make my point, I bring some things:

1. I think we treat render_model as renderToPipeableStream, that's why we use the arch/server/render-rsc-to-stream to do some model response tests.
2. We can pass any JSON-like values to React method renderToPipeableStream:

   const { pipe } = renderToPipeableStream({
   	element: <App />,
   	params: {
   		foo: "bar",
   	},
   	env: "development",
   }); 
   
   /** Result
   2:{"name":"App","env":"Server","key":null,"owner":null,"stack":[["","/Users/pedrolisboa/work/server-reason-react/arch/server/render-rsc-to-stream.js",51,11]],"props":{}}
   1:D"$2"
   1:["$","div",null,{"className":"container","children":["$","link",null,{"rel":"stylesheet","href":"bootstrap.min.css","precedence":"high"},"$2",[["App","/Users/pedrolisboa/work/server-reason-react/arch/server/render-rsc-to-stream.js",47,4]],1]},"$2",[],1]
   0:{"element":"$1","params":{"foo":"bar"},"env":"development"}
   */

3. The one that makes sense to only receive React.element is the render_html, which we treat similar as the renderToReadableStream:

   const { pipe } = renderToPipeableStream({
   	element: <App />,
   	params: {
   		foo: "bar",
   	},
   	env: "development",
   });
   
   /** Result
   error: Objects are not valid as a React child (found: object with keys {element, bootstrapScriptContent, params, env}). If you meant to render a collection of children, use an array instead.
   */

4. We have on React a sample of JSON-like usage of renderToPipeableStream: https://github.com/facebook/react/blob/ea4899e13f9e29815321e3cac70fa08bb8ed790a/fixtures/flight/server/region.js#L126-L131
5. I think we should have this "complex-structure" behavior so we can send more info than only the React.element on cases like navigation