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

js/js.translator/testData/box/delegation/onObject.kt

@@ -0,0 +1,23 @@
+package foo
+
+interface T {
+    fun foo(): String
+}
+
+class TImpl(val v: String) : T {
+    override fun foo() = v
+}
+
+class A {
+    companion object : T by TImpl("A.Default")
+}
+
+object B : T by TImpl("B")
+
+
+fun box(): String {
+    assertEquals("A.Default", A.foo())
+    assertEquals("B", B.foo())
+
+    return "OK"
+}