iOS: circular references in require don't work

While Android's require implementation is able to handle circular references - iOS is not.

This is due to the underlying implementations - where Android is written in JS and mimics Node.js, while iOS is native. There's multiple possible solutions here:

• Use rollup under the hood on apps as part of our build process.
• Migrate iOS to use a shared require implementation with Android

I personally prefer the second, but it'd take some re-architecting of how iOS starts up - and it's unclear to me how we'd tweak Android to use a require implementation under common rather than the one baked into the the runtime (the JS is baked in as bytes and executed early).