Solr Bundle composer.json had been aligned with best practices recently, by moving Test namespaces to autoload-dev property.

This caused unforeseen side effect - running integration tests from a root-package (e.g. ezpublish-kernel), where Solr Bundle is a dependency, is no longer possible, because SetupFactory became part of autoload-dev.
According to the Composer doc autoload-dev is loaded only for root-package, not dependencies.

Steps to reproduce:
1. Start Solr with multicore setup.
2. Clone ezpublish-kernel repository.
3. Set env variable COMPOSER_ROOT_VERSION=dev-master (to avoid any dependency constraints issues).
4. Perform composer install.
5. Perform composer req ezsystems/ezplatform-solr-search-engine:^1.3.0@dev
6. Run phpunit -c phpunit-integration-legacy-solr.xml