feat: Allow ReactNode as children/content of the Toast - closes #6038

[Rados51]

Closes #6038

✅ Pull Request Checklist:

• [x] Included link to corresponding React Spectrum GitHub Issue.
• [x] Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• [x] Filled out test instructions.
• [x] Updated documentation (if it already exists for this component).
• [x] Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

yarn jest