JS: refactor generation of functions with optional parameters. Fix #KT-7302, #KT-13888

js/js.translator/testData/box/multiModule/interfaceMethodWithDefaultParameter.kt

@@ -0,0 +1,13 @@
+// MODULE: lib
+// FILE: lib.kt
+public interface I {
+    public fun f(p: String = "O"): String
+}
+
+// MODULE: main(lib)
+// FILE: main.kt
+public class C : I {
+    override fun f(p: String) = p + "K"
+}
+
+fun box() = C().f()