layers: Use the instance chain for entrypoints with instance

Also add to instance dispatch table CreateInstance and GetGlobalExtensionInfo
diff --git a/layers/mem_tracker.cpp b/layers/mem_tracker.cpp
index 20a69c3..ced65d4 100644
--- a/layers/mem_tracker.cpp
+++ b/layers/mem_tracker.cpp
@@ -2030,7 +2030,7 @@
     if (g_actionIsDefault) {
         g_debugAction = VK_DBG_LAYER_ACTION_CALLBACK;
     }
-    VkResult result = nextTable.DbgRegisterMsgCallback(instance, pfnMsgCallback, pUserData);
+    VkResult result = nextInstanceTable.DbgRegisterMsgCallback(instance, pfnMsgCallback, pUserData);
     return result;
 }
 
@@ -2059,7 +2059,7 @@
             g_debugAction = (VK_LAYER_DBG_ACTION)(g_debugAction & ~((uint32_t)VK_DBG_LAYER_ACTION_CALLBACK));
         }
     }
-    VkResult result = nextTable.DbgUnregisterMsgCallback(instance, pfnMsgCallback);
+    VkResult result = nextInstanceTable.DbgUnregisterMsgCallback(instance, pfnMsgCallback);
     return result;
 }