chore: Improve phpunit performance

[SystemKeeper]

Summary

• Updates PHPUnit to 11.5.56 (was still at 11.5.50 and one of the features is not available there)
• Fixes issues with overwriting system configs and not properly resetting them
• Ensures that the appstore test does not actually make an request
• Removes a leftover user from ApiV1ControllerTest
• Logs the slowest test to CI summary for further inspection
• Sets hashing values in preseed-config.php to improve performance on CI

PHPUnit 32bit seem unrelated, since they also happen on master: https://github.com/nextcloud/server/actions/runs/31857387353/job/94944615074 ?

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[come-nc]

Looks good apart from my feedback on the script.
Would it be possible to detect/block all outgoing HTTP requests from tests?

[come-nc]

Top 30 slowest classes (sum of its tests)
        sum   tests   mean(ms)  class
     55.93s      57     981.28  ApiV1ControllerTest
     49.13s      57     861.90  CommandTest
     30.01s      10    3000.91  OCA\Encryption\Tests\Command\FixEncryptedVersionTest

Any idea why the first two here are listed without namespace?

[come-nc]

Any idea why the first two here are listed without namespace?

Namespace is actually missing from the file -_-

[SystemKeeper]

Would it be possible to detect/block all outgoing HTTP requests from tests?

Good question, that would actually be interesting 🤔

[SystemKeeper]

/backport to stable34