bug: rootParam Ignored When Using Ion-Router

### Prerequisites

- [X] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/.github/CONTRIBUTING.md#creating-an-issue).
- [X] I agree to follow the [Code of Conduct](https://ionicframework.com/code-of-conduct).
- [X] I have searched for [existing issues](https://github.com/ionic-team/ionic-framework/issues) that already report this problem, without success.

### Ionic Framework Version

- [ ] v4.x
- [X] v5.x
- [ ] v6.x

### Current Behavior

The `rootParams` parameter for `ion-nav` can be used to pass parameters to the root page (which has been defined using the `root` attribute). When the `root` attribute is removed from the `ion-nav` tag and an `ion-router` element is used to determine the root page based on the URL, the `rootParams` parameter for `ion-nav` is ignored.

[This fiddle](https://jsfiddle.net/fL7rdvjp/1/) is an example of the use of `rootParams` when the root page is specified using the `ion-nav` `root` attribute.

[This fiddle](https://jsfiddle.net/fL7rdvjp/2/) is an example of how the `rootParams` parameter cannot be read when an `ion-router` element is used to determine the root page.

### Expected Behavior

The first page should have the contents `a: 1, b: 2`

### Steps to Reproduce

Use the following HTML body:
```html

```

WIth the following JavaScript:
```javascript
const nav = document.querySelector('ion-nav');

class NewPage extends HTMLElement {
async connectedCallback() {
this.innerHTML = `






Root Page

a: ${this.a}, b: ${this.b}



New Page

`;

const btn = this.querySelector('ion-button');
btn.addEventListener('click', () => {
nav.push('new-page', { a: this.a + 1, b: this.b + 1});
})
}
}
customElements.define('new-page', NewPage);

nav.rootParams = { a: 1, b: 2 };
```

The root page (or first page that is displayed) will have the contents `a: undefined, b: undefined`, which indicates that `rootParams` was either unused or overwritten.

### Code Reproduction URL

_No response_

### Ionic Info

_No response_

### Additional Information

_No response_