yield on delete so lavinmq doesnt freeze during delete (#859)

Yields during MessageStore#delete so that LavinMQ does not freeze while deleting large queues.

src/lavinmq/amqp/queue/message_store.cr

@@ -195,11 +195,17 @@ module LavinMQ
 
       def delete
         close
-        @segments.each_value { |f| @replicator.try &.delete_file(f.path); f.delete }
-        @acks.each_value { |f| @replicator.try &.delete_file(f.path); f.delete }
+        @segments.each_value { |f| delete_file(f) }
+        @acks.each_value { |f| delete_file(f) }
         FileUtils.rm_rf @queue_data_dir
       end
 
+      def delete_file(file)
+        @replicator.try &.delete_file(file.path)
+        file.delete(raise_on_missing: false)
+        Fiber.yield
+      end
+
       def empty?
         @size.zero?
       end