BREAKING CHANGE
Since `next export` has been printing a deprecation warning since https://github.com/vercel/next.js/pull/47376, its safe to remove in semver-major.
The upgrade path is to simply add `output: 'export'` in `next.config.js` - everything will continue to work the same.
This config greatly improves the `next dev` experience today. And in the future, it will improve performance of `next build` because we no longer need to do two passes (build then export).
Skips additional production-only tests.
Follow-up to #56089.
In this PR I went through all of `test/integration` looking for `nextBuild(` and added the skipping logic.
This PR builds on the work from @hattakdev (PR went stale: https://github.com/vercel/next.js/pull/14499) and adds a new `integration` test for the new warning.
## Bug
- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [x] Errors have helpful link attached, see `contributing.md`
## To run locally
1. `pnpm build`
2. `pnpm testonly test/integration/export-getInitialProps-warn/test/index.test.js`
Fixes#13946
## Notes
<details>
<summary>Click to toggle see</summary>
I know the `contributing.md` doc said to avoid adding new tests to `integration`. It also said new tests should be written in TypeScript.
I wasn't sure where to put the tests for this so I went with `integration`. I also didn't see many other tests written in TS in this part of the codebase so I stuck with `.js`.
</details>
Co-authored-by: JJ Kasper <22380829+ijjk@users.noreply.github.com>
