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

js/js.translator/testData/box/callableReference/property/delegatedMutable.kt

@@ -0,0 +1,27 @@
+// This test was adapted from compiler/testData/codegen/box/callableReference/property/.
+package foo
+
+import kotlin.reflect.KProperty
+
+object Delegate {
+    var value = "lol"
+
+    operator fun getValue(instance: Any?, data: KProperty<*>): String {
+        return value
+    }
+
+    operator fun setValue(instance: Any?, data: KProperty<*>, newValue: String) {
+        value = newValue
+    }
+}
+
+var result: String by Delegate
+
+fun box(): String {
+    val f = ::result
+    if (f.get() != "lol") return "Fail 1: {$f.get()}"
+    Delegate.value = "rofl"
+    if (f.get() != "rofl") return "Fail 2: {$f.get()}"
+    f.set("OK")
+    return f.get()
+}