Add sample(_) and sample(_,_) to Random.

test/random/sample_one.wren

@@ -0,0 +1,20 @@
+import "random" for Random
+
+var random = Random.new(12345)
+
+// Single element list.
+System.print(random.sample(["single"])) // expect: single
+
+// Should choose all elements with roughly equal probability.
+var list = ["a", "b", "c", "d", "e"]
+var histogram = {"a": 0, "b": 0, "c": 0, "d": 0, "e": 0}
+for (i in 1..1000) {
+  var sample = random.sample(list)
+  histogram[sample] = histogram[sample] + 1
+}
+
+System.print(histogram.count) // expect: 5
+for (key in histogram.keys) {
+  var error = (histogram[key] / (1000 / list.count) - 1).abs
+  if (error > 0.2) System.print("!!! %(error)")
+}