Util: Revert allow setting instance pointer manually

This is unnecessary as the allocation + placement new works.

src/ruc/format/formatter.h

@@ -331,6 +331,8 @@ struct Formatter<Specifier> : Formatter<std::nullptr_t> {
 
 } // namespace ruc::format
 
+using ruc::format::Formatter;
+
 #if 0
 
 TODO:

src/ruc/singleton.h

@@ -46,13 +46,6 @@ public:
 protected:
 	Singleton() {}
 
-	// Hack: in certain situations the instance needs to be set early
-	static void set(T* instance)
-	{
-		VERIFY(!s_instance, "singleton already exists");
-		s_instance = instance;
-	}
-
 	// Constructor token
 	struct s {};