Propagate relative path through to IR

[headius]

For various reasons, we want to propagate the original relative path of required/loaded Ruby files through to IR:

• To be able to report the relative path rather than the absolute path in traces and debugging
• To formulate a simpler class name for JIT

I started an attempt at this by propagating it from the LoadService through all the various interfaces to IRRootScope and the JIT, but I'm taking a step back until I figure out if this is the right approach for JVM debugging:

https://gist.github.com/headius/0bf47e90d121b48293d64e7a513bdc99