Refactored tests for switch optimization of When expression

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

@@ -0,0 +1,34 @@
+fun exhaustive(x: Int): Int {
+    var r: Int
+    when (x) {
+        1 -> r = 1
+        2 -> r = 2
+        3 -> r = 3
+        else -> r = 4
+    }
+
+    return r
+}
+
+fun nonExhaustive(x: Int): Int {
+    var r: Int = 4
+    when (x) {
+        1 -> r = 1
+        2 -> r = 2
+        3 -> r = 3
+    }
+
+    return r
+}
+
+fun box(): String {
+    var result = (0..3).map(::exhaustive).makeString()
+
+    if (result != "4, 1, 2, 3") return "exhaustive:" + result
+
+    result = (0..3).map(::nonExhaustive).makeString()
+
+    if (result != "4, 1, 2, 3") return "non-exhaustive:" + result
+    return "OK"
+}
+