Better ToastList's API to support adding exit animation to toasts with motion

### Provide a general summary of the feature here

The current API of [ToastRegion](https://react-spectrum.adobe.com/react-aria/Toast.html) (and ToastList) is hard to add exit animation with [motion](https://motion.dev/docs/react).

The key conflict is that motion requires animated elements must be wrapped by `` directly, to play exit animation before elements unmounting. But ToastList wraps all toasts with a `

` element now without an API to customize the wrapper.

### 🤔 Expected Behavior?

Can use motion's declarative API animate toasts easily.

### 😯 Current Behavior

It's impossible (as far as I know) to add exit animation to toasts with motion.

### 💁 Possible Solution

_No response_

### 🔦 Context

Animate toasts' exiting with motion.

### 💻 Examples

```jsx
{/* not working */}


{({ toast }) => (



{toast.content.title}
{toast.content.message}






)}


```

or

```jsx

{/* not working */}


{({ toast }) => (



{toast.content.title}
{toast.content.message}






)}



```

### 🧢 Your Company/Team

_No response_

### 🕷 Tracking Issue

_No response_

Start by reading the ToastRegion and ToastList APIs referenced in the issue, then reproduce the two motion examples to confirm how the current wrapper prevents exit animation. Done means the API supports declarative toast exit animations with motion while preserving the existing toast behavior.

Written by the indexing model from the issue text.