Improve hydration efficiency

[leo]

At the moment, every initial page load (does not subsequent transitions) causes 2 renders:

One for the initial HTML markup, and one for the JSX stream used for the hydration.

We'd like to instead inline the JSX stream into the HTML markup, to make it a single render.

[leo]

We would likely update our JSX renderer to generate both HTML and JSX at the same time, so that we don't need to convert the JSX to HTML.