Changed MaterialAsset::GetPropertyValues to not auto-finalize. Client code must call Finalize manually. It's better to avoid unexpected side-effects from a const getter function.

In some cases it may be acceptable to do non-const things in a const function as long as it is only manipulating internal data, and the public facing API returns the same values as before. But in this case, the IsFinalized function is a public facing API that would have a different result after GetPropertyValues was called.

I also updated a couple other minor things from code review feedback.

Signed-off-by: santorac <55155825+santorac@users.noreply.github.com>

Gems/Atom/RPI/Code/Source/RPI.Reflect/Material/MaterialAsset.cpp

@@ -199,10 +199,7 @@ namespace AZ
 
         const AZStd::vector<MaterialPropertyValue>& MaterialAsset::GetPropertyValues() const
         {
-            // This can't be done in MaterialAssetHandler::LoadAssetData because the MaterialTypeAsset isn't necessarily loaded at that point.
-            // And it can't be done in PostLoadInit() because that happens on the next frame which might be too late. So we finalize just-in-time
-            // when properties are accessed.
-            const_cast<MaterialAsset*>(this)->Finalize();
+            AZ_Error(s_debugTraceName, IsFinalized(), "MaterialAsset must be finalized before its property values can be accessed");
 
             return m_propertyValues;
         }