Coordination: Upgrade to PHP 8.2 - 8.4 and PHPUnit 11

[mk-mxp]

This is what I think must be done:

• Add PHP 8.4 to the CI of the track and allow it to fail
• Add PHPUnit 11 to the CI of the track and allow it to fail
• Use PHPUnit attributes, not annotations (annotations are deprecated, but still available)
  • Update test generator to produce attributes not annotations
  • Convert tests from annotations to attributes. Use rector/rector for that
• Fix the problems that occur with PHP 8.4 and PHPUnit 11
  • Measure performance when using PHP 8.4 (look at alphametics!)
  • Check the CI test to catch tests that would fail due to the runtime limit set by Exercism infrastructure. Uses timeout 54s <command> as a process based limit per exercise (3x 18 seconds, see forum for calculation details)
• Prepare the PHP test-runner to upgrade to PHP 8.4 / PHPUnit11: Coordination: Prepare for students code using PHP 8.4 php-test-runner#150
• Prepare the PHP representer to upgrade to PHP 8.4: Coordination: Prepare for students code using PHP 8.4 php-representer#297
• Do the actual switch to PHP 8.2 - 8.4 and PHPUnit 11 as the production versions
  • Merge test runner upgrade PR
  • Update student facing documentation
  • Remove PHP 8.1 / PHPUnit 10 from CI, add PHP8.2/8.3 to PHPUnit11 workflow
• Revert performance workaround in "robot-name" exercise (requires PHPUnit >= 11)

In the whole process, try to avoid re-running the representer and not to trigger re-testing all community solutions. These are very costly to Exercism.

FYI: @tomasnorre @homersimpsons

[homersimpsons]

PHPUnit 11

Note that PHPUnit 12 was released earlier this year https://phpunit.de/announcements/phpunit-12.html and is compatible with PHP 8.4, so it may be better to upgrade to this latest version directly.

[mk-mxp]

@homersimpsons PHPUnit 12 does not support PHP8.2, which is the minimum we want to support. Maybe we can discuss later, if we step away from the "3 latest minor PHP versions" principle. Right now, PHPUnit 11 is the only PHPUnit version suitable for the range of PHP 8.2 - 8.4.