Issue #3423942: Enable testing with GitLab CI

.cspell-project-words.txt

.gitlab-ci.yml

conditional_fields.install

conditional_fields.links.menu.yml

conditional_fields.module

conditional_fields.permissions.yml

conditional_fields.services.yml

css/conditional_fields.admin.css

phpstan-baseline.neon

phpstan.neon

src/ConditionalFieldsElementAlterHelper.php

src/ConditionalFieldsFormHelper.php

src/ConditionalFieldsHandlersManager.php

src/Conditions.php

src/DependencyHelper.php

src/Form/ConditionalFieldDeleteForm.php

src/Form/ConditionalFieldDeleteFormTab.php

src/Form/ConditionalFieldEditForm.php

src/Form/ConditionalFieldForm.php

src/Plugin/conditional_fields/handler/Checkbox.php