Some evaluator simplifications

[neunenak]

This PR modifies some of the methods on Evaluator that accept a large number of arguments to instead accept a RecipeContext, which already contains most of those arguments, which allows the call sites to be more concise.

It also deduplicates some of the code around running recipe dependencies, and replaces a mutable variable update with a fold expression.

[casey]

Nice, this is a good refactor. I took it a step further by just having the RecipeContext (now ExecutionContext, because it's used all over the place) be a field on the evaluator. This required some tweaking, in particular, there was a scope that was created outside a call to the evaluator that is now created inside the evaluator.