[Bug] Could not initialize ember app in shadow root node

### 🐞 Describe the Bug

If I trying to initialize ember app on shadow dom root, and it's not working.

```js
class MyApp extends HTMLElement {
constructor() {
super();
this.shadow = this.attachShadow({ mode: 'open' });
}
connectedCallback() {
createEmberApp(this.shadow);
}
}

customElements.define('my-app', MyApp);
```

### 😕 Actual Behavior

```
vendor.js:32566 Uncaught TypeError: Cannot read property 'contains' of undefined
at Class.setup (vendor.js:32566)
at Class.setupEventDispatcher (vendor.js:34140)
at Class._bootSync (vendor.js:34064)
at App.didBecomeReady (vendor.js:35128)
at invoke (vendor.js:59932)
at Queue.flush (vendor.js:59823)
at DeferredActionQueues.flush (vendor.js:60020)
at Backburner._end (vendor.js:60554)
at Backburner.end (vendor.js:60304)
at Backburner._run (vendor.js:60609)
```


Because shadowRoot does not have class list

If I'm patching it, like:

```js
class MyApp extends HTMLElement {
constructor() {
super();
this.shadow = this.attachShadow({ mode: 'open' });
this.shadow.classList = {
contains: () => { return false }
};
}
connectedCallback() {
createEmberApp(this.shadow);
}
}

customElements.define('my-app', MyApp);
```

I'm getting next error:

```
vendor.js:32571 Uncaught TypeError: Cannot read property 'classList' of null
at vendor.js:32571
at Class.setup (vendor.js:32579)
at Class.setupEventDispatcher (vendor.js:34140)
at Class._bootSync (vendor.js:34064)
at App.didBecomeReady (vendor.js:35128)
at invoke (vendor.js:59932)
at Queue.flush (vendor.js:59823)
at DeferredActionQueues.flush (vendor.js:60020)
at Backburner._end (vendor.js:60554)
at Backburner.end (vendor.js:60304)
```

from:


If I'm appending DIV into shadow root and use it as rootNode for ember APP:

```js
class MyApp extends HTMLElement {
constructor() {
super();
this.shadow = this.attachShadow({ mode: 'open' });
this.shadow.classList = {
contains: () => { return false }
};
}
connectedCallback() {
const node = document.createElement('div');
this.shadow.appendChild(node);
createEmberApp(node);
}
}
```

code works fine, but once I remove "shadow patch", it still failing:

with:


To get it working, I have to append one more div into shadow root, like:

```js
class MyApp extends HTMLElement {
constructor() {
super();
this.shadow = this.attachShadow({ mode: 'open' });
}
connectedCallback() {
const node = document.createElement('div');
const appDiv = document.createElement('div');
node.appendChild(appDiv);
this.shadow.appendChild(node);
createEmberApp(appDiv);
}
}
```

### 🤔 Expected Behavior

Ember app creation should work just fine for shadow dom ROOT node.

### 🌍 Environment

- Ember: 3.28

### ➕ Additional Context

Code: https://github.com/emberjs/ember.js/blob/a3a299cd66940bdef1531e89b94f120584119ae3/packages/%40ember/-internals/views/lib/system/event_dispatcher.js#L161

Could we check app's rootNode for `nodeType = 11` or `nodeName = "#document-fragment` to skip this chain of checks?