feat: Remove that unstable imports that we can from the libs

[KATT]

Describe the feature you'd like to request

We use a bunch of imports from @trpc/server/unstable-core-do-not-import.

Describe the solution you'd like to see

We should prefer using @trpc/server whenever we can

• [ ] @trpc/next - #5485
• [ ] @trpc/react-query
• [ ] @trpc/client

Describe alternate solutions

Create a @trpc/server/plugin entrypoint or something that can export explicit stuff for plugins

Additional information

No response

👨‍👧‍👦 Contributing

• [X] 🙋‍♂️ Yes, I'd be down to file a PR implementing this feature!

Funding

• You can sponsor this specific effort via a Polar.sh pledge below
• We receive the pledge once the issue is completed & verified