[JS IR BE] Support Enum::values

compiler/testData/codegen/box/enum/defaultCtor/constructorWithVararg.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 enum class Test(vararg xs: Int) {
     OK;
     val values = xs

compiler/testData/codegen/box/enum/defaultCtor/secondaryConstructorWithVararg.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 enum class Test(val x: Int, val str: String) {
     OK;
     constructor(vararg xs: Int) : this(xs.size + 42, "OK")