feat: add sample(list) and sample(list, count) methods to Random class with two sampling algorithms

test/random/sample_count_all.wren

@@ -0,0 +1,19 @@
+import "random" for Random
+
+var random = Random.new(12345)
+
+// Should choose all elements with roughly equal probability.
+var list = ["a", "b", "c"]
+var histogram = {}
+for (i in 1..5000) {
+  var sample = random.sample(list, 3)
+  var string = sample.toString
+  if (!histogram.containsKey(string)) histogram[string] = 0
+  histogram[string] = histogram[string] + 1
+}
+
+System.print(histogram.count) // expect: 6
+for (key in histogram.keys) {
+  var error = (histogram[key] / (5000 / 6) - 1).abs
+  if (error > 0.1) System.print("!!! %(error)")
+}