* Read the proper page file from either pages directory or from node_modules (inernal pages like _app, _document)
* Only reading page runtime when `reactRoot` is enabled, reduce time for react 17 apps
Partially implements #31317 and #31506. There're also some trade-offs made with this PR: since we can't know if a certain runtime will be used or not beforehand, we have to start both runtime compilers (Node.js and Edge) and then generate entrypoints correspondingly.
Note that with this PR, the global runtime is still required to use the per-page runtime.
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes by running `yarn lint`
