layers: Rework include dependencies

This change removes the assumption that vk_layer.h will include
vk_layer_dispatch_table.h, since it will be removed from vk_layer.h
in the near future.

Change-Id: I082ccc52c3cb8257bf57342404d52dd737009b4b
diff --git a/layers/vk_layer_logging.h b/layers/vk_layer_logging.h
index 2771711..9af840e 100644
--- a/layers/vk_layer_logging.h
+++ b/layers/vk_layer_logging.h
@@ -30,6 +30,7 @@
 #include "vulkan/vk_layer.h"
 #include "vk_object_types.h"
 #include "vk_validation_error_messages.h"
+#include "vk_layer_dispatch_table.h"
 #include <signal.h>
 #include <cinttypes>
 #include <stdarg.h>