Quick-fix for header without implementation + a set of tests #KT-14908 Fixed

idea/testData/multiModuleQuickFix/enum/header/header.kt

@@ -0,0 +1,17 @@
+// "Create header class implementation for platform JS" "true"
+
+header enum class <caret>MyEnum {
+    FIRST,
+    SECOND,
+    LAST;
+
+    val num: Int
+
+    companion object {
+        fun byNum(num: Int): MyEnum = when (num) {
+            1 -> FIRST
+            2 -> SECOND
+            else -> LAST
+        }
+    }
+}

idea/testData/multiModuleQuickFix/enum/header/header.kt.after

@@ -0,0 +1,17 @@
+// "Create header class implementation for platform JS" "true"
+
+header enum class MyEnum {
+    FIRST,
+    SECOND,
+    LAST;
+
+    val num: Int
+
+    companion object {
+        fun byNum(num: Int): MyEnum = when (num) {
+            1 -> FIRST
+            2 -> SECOND
+            else -> LAST
+        }
+    }
+}

idea/testData/multiModuleQuickFix/enum/js/myEnum.kt

@@ -0,0 +1 @@
+// MyEnum: to be implemented

idea/testData/multiModuleQuickFix/enum/js/myEnum.kt.after

@@ -0,0 +1,17 @@
+// MyEnum: to be implemented
+impl enum class MyEnum {
+    FIRST,
+    SECOND,
+    LAST;
+
+    companion object {
+        fun byNum(num: Int): MyEnum = when (num) {
+            1 -> FIRST
+            2 -> SECOND
+            else -> LAST
+        }
+    }
+
+    impl val num: Int
+        get() = TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
+}