JS backend: move patternMatching tests to expression/when

js/js.translator/testData/expression/when/cases/whenValue.kt

@@ -0,0 +1,17 @@
+package foo
+
+fun box(): Boolean {
+    var a = 4
+    when(a) {
+        3 -> {
+            a = 10;
+        }
+        4 -> {
+            a = 20;
+        }
+        else -> {
+            a = 30;
+        }
+    }
+    return (a == 20)
+}