Fix initialization order of enum with companion object in JS BE

Make enum entries initialize before companion object. This helps
in situation when companion object initializer refers to enum fields.
JVM be generates <clinit> method which first initializes all enum fields
and then runs companion object initializer. This commit introduces the
similar behaviour in JS BE. The old behaviour was: initialize companion
object in constructor. In enum, constructor is called to initialize
enum fields, so previously companion object was initialized first,
which is incorrect.

See KT-16745

compiler/testData/codegen/box/enum/enumCompanionInit.kt

@@ -0,0 +1,46 @@
+var result = ""
+
+enum class E(a: String) {
+    X("x"),
+    Y("y");
+
+    init {
+        result += "E.init($a);"
+    }
+
+    companion object {
+        init {
+            result += "E.companion.init;"
+            val value = E.values()[0].name
+            result += "$value;"
+        }
+    }
+}
+
+enum class F(a: String) {
+    X("x"),
+    Y("y");
+
+    init {
+        result += "F.init($a);"
+    }
+
+    companion object {
+        init {
+            result += "F.companion.init;"
+        }
+
+        fun foo() {
+            result += "F.foo();$X;"
+        }
+    }
+}
+
+fun box(): String {
+    val y = E.Y
+    result += "${y.name};"
+    F.foo()
+    if (result != "E.init(x);E.init(y);E.companion.init;X;Y;F.init(x);F.init(y);F.companion.init;F.foo();X;") return "fail: $result"
+
+    return "OK"
+}