Write an OpenRewrite rule to migrate to Rhino 2.0

With the current work on the "master" branch we have finally reached the point where existing Rhino code will need to change, specifically to use the new VarScope class to represent the scope in every call instead of Scriptable. This is a big change, although one that doesn't require a ton of thinking!

OpenRewrite is a great framework well-suited to applying these kinds of changes automatically -- we recently used it in this project to convert from Junit 4 to 5, for example. It accomplished this deterministic task with much less drama and prompting and a lot less money spent than trying to solve that same problem using your favorite LLM.