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/network/Socket.cpp

@@ -975,7 +975,7 @@ std::vector<std::unique_ptr<INetworkEndpoint>> GetBroadcastAddresses()
     return baddresses;
 }
 
-namespace Convert
+namespace OpenRCT2::Convert
 {
     uint16_t HostToNetwork(uint16_t value)
     {
@@ -986,6 +986,6 @@ namespace Convert
     {
         return ntohs(value);
     }
-} // namespace Convert
+} // namespace OpenRCT2::Convert
 
 #endif