NFC: remote queue domestication plumbing

These are, at present, just identity functions in the right places.

src/mem/corealloc.h

@@ -421,13 +421,15 @@ namespace snmalloc
     handle_message_queue_inner(Action action, Args... args)
     {
       bool need_post = false;
+      auto domesticate = [](FreeObject::QueuePtr<capptr::bounds::Alloc> p)
+                           SNMALLOC_FAST_PATH_LAMBDA { return p; };
       for (size_t i = 0; i < REMOTE_BATCH; i++)
       {
         auto p = message_queue().peek();
         auto& entry = SharedStateHandle::Pagemap::get_metaentry(
           backend_state_ptr(), snmalloc::address_cast(p));
 
-        auto r = message_queue().dequeue(key_global);
+        auto r = message_queue().dequeue(key_global, domesticate);
 
         if (unlikely(!r.second))
           break;

src/mem/remoteallocator.h

@@ -102,13 +102,12 @@ namespace snmalloc
     /**
      * Returns the front message, or null if not possible to return a message.
      */
+    template<typename Domesticator>
     std::pair<
       FreeObject::HeadPtr<capptr::bounds::Alloc, capptr::bounds::Alloc>,
       bool>
-    dequeue(const FreeListKey& key)
+    dequeue(const FreeListKey& key, Domesticator domesticate)
     {
-      auto domesticate = [](FreeObject::QueuePtr<capptr::bounds::Alloc> p)
-                           SNMALLOC_FAST_PATH_LAMBDA { return p; };
       invariant();
       FreeObject::HeadPtr<capptr::bounds::Alloc, capptr::bounds::Alloc> first =
         domesticate(front);