Setup SSR testing

[thetarnav]

Having automatic tests specifically for SSR should help ensure that solid-aria can be used with solid-start without trouble.
Not that it's certain that it'll run, we've seen that there are a lot of random things, especially with jsx transform that could go wrong. But the API itself should benefit from this.

• moved some of the configs to new /configs dir — frees some space in the root
• Added jest config & setup files specifically for ssr
• Added ssr tests to label package (It's a only a start😄)
• Fixed createSlotId to prevent it from accessing DOM APIs on the server.

Should I add a changeset for all packages, or only the updated utils?

[changeset-bot]

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Latest commit: 489f9f1

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[fabien-ml]

I don't think there is a need to release for now, maybe when we have more component related primitives done. I've set the release action manual btw.