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/core/Http.cURL.cpp

@@ -27,7 +27,7 @@
 
 #    define OPENRCT2_USER_AGENT "OpenRCT2/" OPENRCT2_VERSION
 
-namespace Http
+namespace OpenRCT2::Http
 {
     static size_t WriteData(const char* src, size_t size, size_t nmemb, void* userdata)
     {
@@ -161,6 +161,6 @@ namespace Http
         return res;
     }
 
-} // namespace Http
+} // namespace OpenRCT2::Http
 
 #endif