Coordinate track development

Here's what we may do next:

- [x] #793
- [ ] Take forward the PHP test generator(s)
- [ ] Respect for further development: #675
- [ ] Creating new exercises: #663
- [ ] Updating existing tests: #674
- [ ] Merge both test generator approaches into one CLI
- [ ] #703
- [x] #628 The test generator may help with that, too.
- [x] #755 Remove the remaining uses of data providers.
- [ ] Make #578 happen and build on that with new concept exercises
- [ ] Apply #324 when we have 20 concept exercises and practice exercises are in sync with problem specifications
- [ ] Re-work difficulty of the practice exercises and sort them by difficulty in `config.json` (that determines the order on the website)
- [ ] Build better track documentation
- [ ] Track standards Parts: #658
- [ ] Rationals behind standards, design decisions and architectural stuff (e.g. ADRs)
- [ ] add PHP specific information to Exercism documentation
- Put it into directory `contribution/documentation`
- [ ] #629 The test generator will help with that.

Suggestions welcome. Discussions should happen in the [forum, category Building Exercism](https://forum.exercism.org/c/exercism/building-exercism/125). Please mention @mk-mxp and whom it may concern.

I currently dig into [Exercism tasks](https://exercism.org/docs/building/product/tasks) to communicate concrete improvements with GitHub issues and attract other contributors to help.

Things already done:

- [x] Remainders of #652
- [x] Use attributes in the tests (experiment with [Rector](https://packagist.org/packages/rector/rector) for that).
- [x] Update test generator to produce attributes not annotations
- [x] Prepare for smooth upgrading to PHP 8.2 - 8.4 and PHPUnit 11 / 12
- [x] Revert performance workaround in "robot-name" exercise (requires PHPUnit >= 11)
- [x] #684
- [x] #813
- [x] Merge #591 to ease contribution for further developers. @homersimpsons Thanks for kicking that forward.
- [x] #619 Reformat track files using `configlet fmt` to enable smooth creation of new exercises.
- [x] #631 Integrate the [PHP test generator](https://forum.exercism.org/t/poc-for-autogenerated-tests-for-php-track/9692) of @tomasnorre . We are holding it in a sub-directory as a separate composer project, so it is not installed in CI along with the other requirements. Goal is to kickstart new exercises as far as reasonable.
- [x] #630 Add the [missing practice exercises for `#48in24`](https://exercism.org/challenges/48in24/implementation_status). @homersimpsons announced to do that, but everybody may add one
- [x] ~~Drop windows / macOS from the CI. Check with Erik Schierboom, if we can. PHP is not that much platform specific anymore. And Exercism does not have the real troublesome stuff.~~ [Rejected on the forum](https://forum.exercism.org/t/php-stop-running-ci-tests-on-macos-and-windows/10025). MacOS dropped anyways, because it fails too often (auto updates in Homebrew kill PHP installation)
- [x] #667 - but we missed the extended goal to have articles / approaches for it.