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/platform/Platform.Android.cpp

@@ -32,7 +32,7 @@ jmethodID AndroidClassLoader::_findClassMethod;
 // available until after JNI_OnLoad is called.
 static std::shared_ptr<AndroidClassLoader> acl;
 
-namespace Platform
+namespace OpenRCT2::Platform
 {
     std::string GetFolderPath(SPECIAL_FOLDER folder)
     {
@@ -192,7 +192,7 @@ namespace Platform
             AndroidClassLoader::_classLoader, AndroidClassLoader::_findClassMethod,
             env->NewStringUTF(std::string(name).c_str())));
     }
-} // namespace Platform
+} // namespace OpenRCT2::Platform
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* pjvm, void* reserved)
 {