Draft: [TEST] #3638148 Rector composer-based twig set

Part of #3638148: testing whether running Rector's composer-based sets on a Drupal codebase breaks Drupal.

Do not merge. This is a test MR. Generated with Rector 2.8.4 + palantirnet/drupal-rector 1.2.0, using rector-3638148/rector-twig.php from the 3638148-rector-tooling branch (paths: core/, skip list taken from core/phpstan.neon.dist excludePaths).

Each commit applies one Rector rule and lists the files it changed, so a failing test can be traced to a rule from the Commits tab. The last commit adds rector-3638148-twig.json, the full dry-run output. To rebuild the branch, see rector-3638148/README.md on the tooling branch.

Lint jobs will probably fail (coding standards, phpstan baseline); that is expected. The test jobs are the signal.

Result

1 file changed: AddReturnTypeDeclarationRector adds : array to getFunctions()/getFilters() in twig_extension_test.