Update to Nextcloud 25.0.3 and new PortCheck Service

- Push latest supported version of Nextcloud to 25.0.3
- Use new PortCheck backend (shoutout to [@ZendaiOwl](https://github.com/ZendaiOwl))
- Add ncp app for manually clearing the PHP opcache (including file cache)

- Remove deprecated apt package `php-json` and warn users if `php8.2-*` packages are detected on their instance
- Whenever ncp sends a notification, all NC users in the admin group will now receive it (instead of the first admin user)
- Fix bug in ncp-update-nc that would prevent the backup from being restored on error in some cases
- Adjust PHP opcache config to hopefully avoid one source of opcache JIT segmentation fault errors
- Disable PHP opcache for cli usage (so the segmentation faults don't affect ncp tools and ncc commands)
- (docker) Fix display of nextcloud logs in container output in some cases
- (docker) Config files of new ncp apps are now properly installed

- (CI/CD) Include NC updates in update integration tests
- (CI/CD) Improve output formatting and robustness for sd image tests
- (CI/CD) Disable image builds and tests that are known to fail for reasons out of our influence