let betterRenderer import the modules

The module file set moves to its own eu07_modules library: a target can
only consume C++20 modules by linking the target that owns them, and
betterRenderer is a separate add_library. Its project includes become
imports.

CXX_EXTENSIONS must match across the two - a BMI built with -std=c++20
is refused by a unit compiled with -std=gnu++20.

betterRenderer/renderer/include/nvrenderer/nvrenderer.h

@@ -22,14 +22,14 @@
 #include <mutex>
 
 // EU07 includes
-#include <utilities/Classes.h>
-#include <scene/scene.h>
+import eu07.utilities.classes;
+import eu07.simcore;
 
 #include "nvrenderer_enums.h"
 #include "quadtree.h"
-#include "rendering/renderer.h"
+import eu07.rendering.renderer;
 #include "resource_registry.h"
-#include "environment/sky.h"
+import eu07.environment.sky;
 
 namespace Rt {
 struct IRtModel;