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/scripting/ScriptEngine.h

@@ -32,7 +32,7 @@ struct duk_hthread;
 typedef struct duk_hthread duk_context;
 
 class GameAction;
-namespace GameActions
+namespace OpenRCT2::GameActions
 {
     class Result;
 }