feat: migrate slot usages

[dummdidumm]

Now that snippets can fill slots, we can add logic to migrate slot usages

There's some cases where it doesn't look as nice due to indentation but I'm not sure how much time we should invest in that

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[changeset-bot]

🦋 Changeset detected

Latest commit: 7e0c70d

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[trueadm]

Works well for me.