feat(SelectMenu): allows to customize labels

❓ Type of change

• [x] 📖 Documentation (updates to the documentation or readme)
• [ ] 🐞 Bug fix (a non-breaking change that fixes an issue)
• [x] 👌 Enhancement (improving an existing functionality)
• [ ] ✨ New feature (a non-breaking change that adds functionality)
• [ ] 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• [ ] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Avoids to use slots or props to customize labels in SelectMenu.

Would you mind doing the same for InputMenu? This can be done in the same PR. I'd rather keep both components 1:1.

@benjamincanac done in https://github.com/nuxt/ui/pull/2295