Create an in-browser implementation of the integration test harness

[anandthakker]

I think creating an in-browser version of suite_implementation.js would ease / speed up the process of working on shaders and other rendering logic, as it would allow a flow where you load up one of the relevant render tests in the browser, possibly set breakpoints & inspect, possibly use chrome's WebGL debugging extension, and easily refresh to check changes.

[ansis]

This would also let us run all the render tests in all the actual browsers and hopefully catch some browser-specific bugs.

[mourner]

There's also a chance we could then run this on CI using CPU drivers for GL https://github.com/google/swiftshader + headless Chrome

[asheemmamoowala]

This was done in #8584 and cbf6229