Merge branch '8.x-2.x' into 3319045-build-events-assert

...t/existing_correct_fixture/vendor/composer/installed.json

...st/existing_correct_fixture/vendor/composer/installed.php

...Test/missing_installed_php/vendor/composer/installed.json

...tTest/missing_installed_php/vendor/composer/installed.php

...er/tests/fixtures/fake_site/vendor/composer/installed.php

package_manager/tests/src/Kernel/FixtureUtilityTraitTest.php

package_manager/tests/src/Traits/FixtureUtilityTrait.php

tests/src/Kernel/StatusCheck/StagedProjectsValidatorTest.php