refactor: use fold expressions instead of recursive calls in SerializeMany()

Instead of recursively calling `SerializeMany` and peeling off one
argument at a time, use a fold expression. This simplifies the code,
makes it most likely faster because it reduces the number of function
calls, and compiles faster because there are fewer template
instantiations.

Author: martinus

src/serialize.h

@@ -1039,16 +1039,10 @@ class CSizeComputer
     int GetVersion() const { return nVersion; }
 };
 
-template<typename Stream>
-void SerializeMany(Stream& s)
-{
-}
-
-template<typename Stream, typename Arg, typename... Args>
-void SerializeMany(Stream& s, const Arg& arg, const Args&... args)
+template <typename Stream, typename... Args>
+void SerializeMany(Stream& s, const Args&... args)
 {
-    ::Serialize(s, arg);
-    ::SerializeMany(s, args...);
+    (::Serialize(s, args), ...);
 }
 
 template<typename Stream>