Refactored tests for switch optimization of When expression

compiler/testData/codegen/boxWithStdlib/when/switchOptimizationSparse.kt

@@ -0,0 +1,18 @@
+import java.util.ArrayList
+
+fun sparse(x: Int): Int {
+    return when ((x % 4) * 100) {
+        100 -> 1
+        200 -> 2
+        300 -> 3
+        else -> 4
+    }
+}
+
+fun box(): String {
+    var result = (0..3).map(::sparse).makeString()
+
+    if (result != "4, 1, 2, 3") return "sparse:" + result
+    return "OK"
+}
+