Adopt existing namespaces into OpenRCT2 namespace (#22368)

* Put all of TitleSequenceManager into the same namespace

* Move RideConstructionState into the OpenRCT2 namespace

* Adopt existing namespaces into OpenRCT2 namespace

This adds `using namespace OpenRCT2` to compilation units where appropriate,
as a means to get the codebase to compile until these units have been placed
in a namespace of their own.

src/openrct2/object/FootpathSurfaceObject.cpp

@@ -15,6 +15,8 @@
 #include "FootpathEntry.h"
 #include "ObjectRepository.h"
 
+using namespace OpenRCT2;
+
 void FootpathSurfaceObject::Load()
 {
     GetStringTable().Sort();