馃 task: #3592170 Upgrade to PHPStan 2.3.0 and phpstan-phpunit 2.1.0, and fix the new errors

Fons Vandammerequested to merge
issue/canvas-3592170:3592170-upgrade-to-phpstan-23-and-remove-the-phpstanphpstan-phpunit-2021-pin into 1.x

Upgrades phpstan/phpstan to 2.3.0 and phpstan/phpstan-phpunit to 2.1.0. Fixes 10 of the 12 new errors. The other 2 are PHPStan 2.3.0 false positives, ignored inline with a @todo.

AI-Generated: Yes (Used Claude Code to compare PHPStan 2.2.16 and 2.3.0 results, sort real errors from false positives, and write the change).

Testing instructions

  • lint (php) passes
  • Kernel and functional tests pass

Closes #3592170

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