Unify features of constructor and method binding

Constructor and method binding differ in these ways:

* Methods do not support explicit binding (#952)
* Constructors do not support complex types (see broken tests in draft PR #1014)

The known difference is:

* Method handlers are bound to specific overloads. Constructor evaluation currently looks for a constructor with a usable signature (not full overload handling)

The purpose of this issue is to

* Delineate any other differences and similarities
* Unify the code paths

This unification started with the explicit parameter binding work on #952, but will result in changes to fix constructor complex types, and will allow test unification.