fix: improve hydration of altered html

[7nik]

Closes #15337

Add checks that during hydration we retrieve a right node (should also we check nodeName?) and that we didn't cross the hydration marker.
Also, in case of hydration mismatch in svelte:head, remounts only the head instead of the entire app.

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🦋 Changeset detected

Latest commit: 5545894

The changes in this PR will be included in the next version bump.

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Preview: https://svelte-dev-git-preview-svelte-16226-svelte.vercel.app/

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Playground

pnpm add https://pkg.pr.new/svelte@16226

[7nik]

Having #16248, now I wonder if this PR makes sense. Though, I think remounting only the svelte:head is a good thing.