feat(nuxt): automatically generate unique keys for keyed composables

[danielroe]

🔗 Linked issue

resolves nuxt/nuxt#13963, resolves nuxt/nuxt#13951, resolves nuxt/nuxt#13583

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This PR automatically generates fallback keys for useState, useAsyncData, useFetch, useLazyAsyncData and useLazyFetch. If no key is provided by the user, or one can't be used (if, for example, functions are passed in the options to useFetch or useLazyFetch) then the fallback key is used instead.

Fallback keys are unique to the file & line number of the call to one of the keyed composables above. (So if a user uses one of them in their own composable, the fallback key will be shared across all possible calls to this composable, rather than being unique to each call.)

I've also updated the types in the documentation for useAsyncData and useFetch where there were some typos.

Further note: It would be nice to have native support in unplugin for parsing using acorn-compatible AST: unjs/unplugin#90. When that's possible, we can refactor this slightly into a native unplugin rather than just using it as a utility within the webpack builder...

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.
• examples updated

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[pi0]

Perf: We don't need array creation and shift on normal (string, fn, obj?) usage.

We can use a variable swap for (fn, obj?) (is this even valid and handled when magic-keys pluign is not working ?!)

[danielroe]

Yes, this works even if the plugin isn't working, as long as the user provides a key. If they don't, they will get an error message: 'asyncData key must be a string'.

[danielroe]

And you're right, we could swap variables around, but we would lose internal typing for those variables by doing it that way.

[danielroe]

@pi0 Let me know when you plan to review this and I will resolve conflicts.

[pi0]

You can resolve :)

[danielroe]

Redoing merge as we can drop #5710 in this PR. There is no need for a warning as a key is automatically provided in this case.