JS: create new common directory for all generated tests, migrate several tests there

js/js.translator/testData/box/delegateProperty/simple.kt

@@ -0,0 +1,31 @@
+package foo
+
+import kotlin.reflect.KProperty
+
+interface WithNumber {
+    var number: Int
+}
+
+class IncNumber(val inc: Int) {
+    operator fun getValue(withNumber: WithNumber, property: KProperty<*>): Int {
+        return withNumber.number + inc;
+    }
+    operator fun setValue(withNumber: WithNumber, property: KProperty<*>, value: Int) {
+        withNumber.number = value;
+    }
+}
+
+class A : WithNumber {
+    override var number: Int = 5
+    var nextNumber by IncNumber(3)
+}
+
+fun box(): String {
+    if (A().nextNumber != 8) return "A().nextNumber != 8, it: ${A().nextNumber}"
+
+    val a = A()
+    a.nextNumber = 10;
+    if (a.number != 10) return "a.number != 10, it: " + a.number
+    if (a.nextNumber != 13) return "a.nextNumber != 13, it: " + a.nextNumber
+    return "OK"
+}