Address Reducer._printChanges() sendability (#3320)

* Address `Reducer._printChanges()` sendability

Because printing is done on a queue, both `State` and `Action` must be
sendable. While `State` is easy enough to make sendable, it might be a
pain to do so in a large, modularized application. Actions are not
always so easy, but are in simple cases.

Alternately, since this is a debugging affordance:

1. We could forego sendability since all we're doing is hitting it with
   a `Mirror` at the end of the day, and traffic the state/action along
   in a `nonisolated(unsafe)`.

2. We could ditch the queue...but that could affect the performance
   pretty negatively in some cases.

* Unchecked send the debug printing

Sources/ComposableArchitecture/Reducer/Reducers/DebugReducer.swift

@@ -21,13 +21,21 @@ extension Reducer {
 
 private let printQueue = DispatchQueue(label: "co.pointfree.swift-composable-architecture.printer")
 
-public struct _ReducerPrinter<State, Action> {
-  private let _printChange: (_ receivedAction: Action, _ oldState: State, _ newState: State) -> Void
+public struct _ReducerPrinter<State, Action>: Sendable {
+  private let _printChange: @Sendable (
+    _ receivedAction: Action,
+    _ oldState: State,
+    _ newState: State
+  ) -> Void
   @usableFromInline
   let queue: DispatchQueue
 
   public init(
-    printChange: @escaping (_ receivedAction: Action, _ oldState: State, _ newState: State) -> Void,
+    printChange: @escaping @Sendable (
+      _ receivedAction: Action,
+      _ oldState: State,
+      _ newState: State
+    ) -> Void,
     queue: DispatchQueue? = nil
   ) {
     self._printChange = printChange
@@ -77,17 +85,23 @@ public struct _PrintChangesReducer<Base: Reducer>: Reducer {
     ) -> Effect<Base.Action> {
       if let printer = self.printer {
         return withSharedChangeTracking { changeTracker in
-          let oldState = state
+          let oldState = UncheckedSendable(state)
           let effects = self.base.reduce(into: &state, action: action)
           return withEscapedDependencies { continuation in
             effects.merge(
-              with: .publisher { [newState = state, queue = printer.queue] in
+              with: .publisher { [
+                newState = UncheckedSendable(state),
+                action = UncheckedSendable(action),
+                queue = printer.queue
+              ] in
                 Deferred<Empty<Action, Never>> {
                   queue.async {
                     continuation.yield {
                       changeTracker.assert {
                         printer.printChange(
-                          receivedAction: action, oldState: oldState, newState: newState
+                          receivedAction: action.wrappedValue,
+                          oldState: oldState.wrappedValue,
+                          newState: newState.wrappedValue
                         )
                       }
                     }