Add DelayedCall and integrate it into navigator and histogram

- Rename `delayedconnection.h` to `delayed.h`
- Align `delayed_helper::apply()` with `std::apply()`

rtgui/adjuster.h

@@ -19,7 +19,7 @@
 #pragma once
 
 #include "editedstate.h"
-#include "delayedconnection.h"
+#include "delayed.h"
 #include "guiutils.h"
 
 class Adjuster;