Fix phpstan complaints and missing behat in the CI jobs

README.md

features/bootstrap/FeatureContext.php

opt/setup-dev-container.sh

src/Avro/Loader/ChainLoader.php

src/Avro/Loader/DirectoryLoader.php

src/Avro/Loader/FileLoader.php

src/Avro/Loader/Loader.php

src/Avro/Loader/LoaderError.php

src/Avro/Transpiling/ClassName.php

src/Avro/Transpiling/Class_.php

src/Avro/Transpiling/DTO.php

src/Avro/Transpiling/Enum.php

src/Avro/Transpiling/HasTranspiler.php

src/Avro/Transpiling/Namespace_.php

src/Avro/Transpiling/Package.php

src/Avro/Transpiling/Property.php

src/Avro/Transpiling/PropertyLogicalType.php

src/Avro/Transpiling/PropertyName.php

src/Avro/Transpiling/PropertyType.php

src/Avro/Transpiling/TranspileError.php