Add micro bench test about tuples

Author: liufengyun

tests/bench/tuple.scala

@@ -0,0 +1,9 @@
+object Test {
+  val xs0 = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
+  assert(xs0(15) == 16)
+    // 2.787s
+
+  val xs1 = xs0 ++ xs0
+  assert(xs1(31) == 16)
+    // 3.354s
+}