Remove `withSentry` in sentry-nextjs package

[vladanpaunovic]

Problem Statement

As per #5778 we are doing all route wrapping on our own and having withSentry function has a potential to cause confusion and frankly, it becomes a tech debt the moment we promote auto wrapping of nexjs API routes to default SDK behaviour.

Solution Brainstorm

⚠️ this is a breaking change. I propose we schedule this for our v8 release ⚠️

1. Remove the withSentry from sentry-nextjs package
2. Communicate breaking changes in v8 of the SDK.

[lobsterkatie]

Yup, this is the plan.

[AbhiPrasad]

Done with #10549