layers: Consolidate thread-safety header files

Combine thread-safety.h and thread_safety_validation.h to allow for
more code-gen.

Change-Id: I5b6535d550efbc5c45c49c0058fd07b6dc895208
diff --git a/scripts/layer_chassis_generator.py b/scripts/layer_chassis_generator.py
index f36c132..4a9171f 100644
--- a/scripts/layer_chassis_generator.py
+++ b/scripts/layer_chassis_generator.py
@@ -373,7 +373,7 @@
 #include "object_lifetime_validation.h"
 #define OBJECT_LAYER_NAME "VK_LAYER_LUNARG_object_tracker"
 #elif BUILD_THREAD_SAFETY
-#include "thread_safety_validation.h"
+#include "thread_safety.h"
 #define OBJECT_LAYER_NAME "VK_LAYER_GOOGLE_threading"
 #elif BUILD_PARAMETER_VALIDATION
 #define OBJECT_LAYER_NAME "VK_LAYER_LUNARG_parameter_validation"