There's a lot of changes here and surely some rough edges to iron out.
Also, I need to update the docs. But I want to get closer to landing
this so I can build on it.
This is a breaking change because existing imports in user Wren code
that assume the path is relative to the entrypoint file will now likely
fail.
Also, stack trace output and host API calls that take a module string
now need the resolved module string, not the short name that appears in
the import.
