ref(nextjs): Split `withSentryConfig`

[github-actions]

Note

The pull request "ref(nextjs): Split withSentryConfig" was created by @chargome but did not reference an issue. Therefore this issue was created for better visibility in external tools like Linear.

The function became bloated and unreadable. This PR just splits the function and refactors parts into utils.

[linear]

JS-1440

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #18777, which was included in the 10.34.0 release.