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

js/js.translator/testData/box/callableReference/function/classMemberFromExtension.kt

@@ -0,0 +1,15 @@
+// This test was adapted from compiler/testData/codegen/box/callableReference/function/.
+package foo
+
+class A {
+    fun o() = 111
+    fun k(k: Int) = k
+}
+
+fun A.bar() = (A::o)(this) + (A::k)(this, 222)
+
+fun box(): String {
+    val result = A().bar()
+    if (result != 333) return "Fail $result"
+    return "OK"
+}