fix: only use iterator destructuring logic if there's an array pattern

[paoloricciuti]

Closes #15996

The logic introduced in #15813 produce much more chunky code...while this is not really a problem since the generated code should gzip wonderfully we really don't need to use that logic unless there's an ArrayPattern in the declarator.

I've added a snapshot test but I'm not sure is worth having but i can remove it easily if we think it's not worth.

Also this is walking the ObjectPattern because if at any point in the destructure there's an array we need to fall back to what @Ocean-OS introduced for the same reason.

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Preview: https://svelte-dev-git-preview-svelte-16000-svelte.vercel.app/

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Playground

pnpm add https://pkg.pr.new/svelte@16000

[Rich-Harris]

I think we need to revisit #15813 anyway, because in a case like this it's still broken (albeit differently/less so than before)

[paoloricciuti]

I think we need to revisit #15813 anyway, because in a case like this it's still broken (albeit differently/less so than before)

Mmm tbf i don't think it's even possible to have an universal way to deal with iterators because you can do all sort of funky behaviours in them and it boils down to them not being pure.

[Rich-Harris]

Closing in favour of #16015