Fix macro compiler bug in release mode.

[mbrandonw]

Fixes #2824.

There is a Swift compiler/macro bug that causes the compiler to choke on constrained opaque types (e.g. some Reducer<State, Action>) when the State and Action are also generated by the macro. It doesn't happen in all situations, but something about enum reducers exacerbates the problem (perhaps it's cause of the static var body?).

The fix is to just not use opaque types in the macro generated code and instead expand the whole type for the static var body. It's a bit messy, but it works.

[mbrandonw]

These tests were failing on CI before the enum-reducers branch was merged, and in haste I just commented them out because I thought it was due to something else. Well, turns out it was catching the problem this PR fixes. So now we can bring them back.

[mbrandonw]

This is messy code, but it essentially generates a type like this:

ReducerBuilder<Self.State, Self.Action>._Sequence<
  ReducerBuilder<Self.State, Self.Action>._Sequence<
    ReducerBuilder<Self.State, Self.Action>._Sequence<
      Scope<Self.State, Self.Action, Feature1>, 
      Scope<Self.State, Self.Action, Feature2>
    >, 
    Scope<Self.State, Self.Action, Feature3>
  >, 
  Scope<Self.State, Self.Action, Feature4>
>

…from a list of Scope types.