Update QA PHP integration

[lennartvava]

Summary

Updates QA Drupal to use QA PHP 3.0.1 and aligns its Drupal, PHPUnit, and CI compatibility matrix with Drupal 11.4 and Drupal 12.

Changes

• Added district09/qa-php:^3.0 as the shared PHP QA toolchain dependency.
• Removed duplicated direct QA-tool dependencies now supplied by QA PHP.
• Retained direct dependencies required by QA Drupal’s Drupal, Behat, PHPUnit bridge, PHPStan Drupal, TwigCS, and configuration-merging integrations.
• Raised the Drupal core requirement to ^11.4 || ^12.0.
• Removed PHPUnit 10 support; Drupal 11.4 uses PHPUnit 11.5 and Drupal 12 uses PHPUnit 12.5.
• Added PHPUnit 11.5-specific Drupal site and extension XML templates.
• Updated the configuration merger to select the correct Drupal PHPUnit template for the installed PHPUnit major.
• Updated the PHPUnit 12 templates to use the PHPUnit 12.5 XML schema.
• Added test coverage for generated PHPUnit schema selection.
• Updated CI to test Drupal 11.4 on PHP 8.3, 8.4, and 8.5, and Drupal 12 on PHP 8.5.
• Updated README, upgrade notes, and changelog.

Verification

• Composer validation and normalization.
• PHP syntax validation.
• YAML, NEON, and XML configuration validation.
• Focused PHPUnit test suite.
• Diff whitespace validation.