JS: refactor code that copies default methods in interfaces to classes

Als fixes KT-21245

js/js.translator/testData/box/defaultArguments/inheritViaAnotherInterfaceIndirectly.kt

@@ -0,0 +1,32 @@
+// EXPECTED_REACHABLE_NODES: 1147
+interface I {
+    fun foo(x: String = "default"): String = "I.foo($x)"
+}
+
+interface J : I {
+    override fun foo(x: String): String
+}
+
+interface K : J {
+    override fun foo(x: String): String = "K.foo($x)"
+}
+
+class A : I
+
+class B : K
+
+fun box(): String {
+    val a = A()
+    var r = a.foo()
+    if (r != "I.foo(default)") return "fail: A.foo()"
+    r = a.foo("Q")
+    if (r != "I.foo(Q)") return "fail A.foo(Q): $r"
+
+    val b = B()
+    r = b.foo()
+    if (r != "K.foo(default)") return "fail B.foo(): $r"
+    r = b.foo("W")
+    if (r != "K.foo(W)") return "fail B.foo(W): $r"
+
+    return "OK"
+}