`ComponentDialog.asDialogHolderWithContent` should provide decor view as container

This:

```kotlin
    .buildView(overlay.content, envWithOnBack, context)
```

should be this:

```kotlin
    .buildView(overlay.content, envWithOnBack, context, decorView as ViewGroup)
```

But watch out for the perils of resolving `decorView` too early I hate Android. (Note use of our `Dialog.decorView` extension.)