Make debug_check_empty not use statistics

Debug_check_empty now empties the free lists, and checks it empties all the
queues in the allocator.  This does not require statistic tracking to
work anymore.

This additionally can check internal regression that cause leaks that
are not the clients fault.

src/mem/globalalloc.h

@@ -120,32 +120,18 @@ namespace snmalloc
       auto* alloc = Parent::iterate();
 
       bool done = false;
+      bool okay = true;
 
-      size_t non_empty_count = 0;
       while (!done)
       {
         done = true;
         alloc = Parent::iterate();
-        non_empty_count = 0;
+        okay = true;
 
         while (alloc != nullptr)
         {
-          // Destroy the message queue so that it has no stub message.
-          Remote* p = alloc->message_queue().destroy();
-
-          while (p != nullptr)
-          {
-            Remote* next = p->non_atomic_next;
-            alloc->handle_dealloc_remote(p);
-            p = next;
-          }
-
           // Check that the allocator has freed all memory.
-          if (!alloc->stats().is_empty())
-            non_empty_count++;
-
-          // Place the static stub message on the queue.
-          alloc->init_message_queue();
+          alloc->debug_is_empty(&okay);
 
           // Post all remotes, including forwarded ones. If any allocator posts,
           // repeat the loop.
@@ -162,13 +148,18 @@ namespace snmalloc
 
       if (result != nullptr)
       {
-        *result = non_empty_count == 0;
+        *result = okay;
         return;
       }
 
-      if (non_empty_count != 0)
+      if (!okay)
       {
-        error("debug_check_empty: found non-empty allocators");
+        alloc = Parent::iterate();
+        while (alloc != nullptr)
+        {
+          alloc->debug_is_empty(nullptr);
+          alloc = Parent::iterate(alloc);
+        }
       }
 #else
       UNUSED(result);