Use same initialization order in Scenario as Collect

[seadowg]

This switches the initialization order in Scenario to match Collect (FormDef#initialize is called after creating the FormEntryController). It also makes it possible to pass in a custom function for constructing the FormEntryController to allow tests to use plugins (like #addFilterStrategy).

[lognaturel]

This is a really great time to make these kinds of changes since we're just exposing Scenario for the first time as an intentional public interface and we are planning a major version bump 👍

[lognaturel]

Since we're doing a major version bump anyway, what do you think about removing these right away? It's very unlikely there are existing consumers and if there are it's an easy change. We'd just want to make sure to track these breaking changes somewhere so we can document them.

[seadowg]

I'd thought about that, but we'd need to do significant work to move EvaluationContext ownership to FormEntryController (as that's what these methods affect). I gave doing a minimal change (where we still end up with a coupling between FormDef and FormEntryController but the EvaluationContext moves) a go, but it was pretty involved.

[lognaturel]

Ah, ok, I thought it was an easier change that that. Sounds good.