Cleanup global __NEXTAUTH state after unmount

[skirsten]

Re-mounting the component was not reloading the session because the global __NEXTAUTH was not cleaned up on unmount.

Reasoning 💡

#4252 (comment)

Checklist 🧢

• [] Documentation
• [] Tests
• Ready to be merged

Note: If using reactStrictMode: true and using React 18 (vercel/next.js#35822) you will see two api/auth/session requests during next dev

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[ubbe-xyz]

Thanks for the contribution 💚

This is, AFAIK on purpose, so the session is stored in memory so long as the application is running. @balazsorban44 is the one who knows the details of this though, let's wait for his feedback ☕️

[balazsorban44]

Thanks, this sounds good. 👍