JS backend: move patternMatching tests to expression/when

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

@@ -0,0 +1,12 @@
+package foo
+
+
+fun box(): Boolean {
+
+    return (when(1) {
+        2 -> 3
+        1 -> 1
+        else -> 5
+    } == 1)
+
+}