docs: rewrite data fetching section

[clemcode]

❓ Type of change

• 📖 Documentation (updates to the documentation, readme or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ 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

This PR goal is to address some common issues the users are facing after reading the Data Fetching section:

• Lack of understanding of the composables goals and differences
• Reference to ofetch and clarify the $fetch alias
• Composables options and patterns

I tried to not lose anything in the rewrite. Would love some feedback on the new page structure and if it makes it clearer.

[nuxt-studio]

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[danielroe]

Nice work! ❤️