feat: add overloaded IO.print methods accepting 2-16 arguments and printList_ helper

Add 15 static overloads of IO.print in builtin/io.wren and src/wren_io.c, each delegating to a new private printList_ method that iterates over a list of objects. Update all benchmark and test files to use the new multi-argument syntax, removing explicit .toString calls and string concatenation. Add a comprehensive test/io/print.wren verifying single-argument return value, multi-argument null return, and concatenation of up to 16 arguments.

test/class/name_inside_body.wren

@@ -1,10 +1,10 @@
 class Foo {
   static sayName {
-    IO.print(Foo.toString)
+    IO.print(Foo)
   }
 
   sayName {
-    IO.print(Foo.toString)
+    IO.print(Foo)
   }
 
   static toString { "Foo!" }