tests: Add type hints

tests/SigningTestCase.php

tests/Utils/ClearStateTestCase.php

tests/Utils/ExitTestException.php

tests/Utils/ReduceSpillOverTest.php

tests/Utils/StateClearer.php

tests/_autoload_modules.php

tests/lib/SimpleSAML/Auth/SimpleTest.php

tests/lib/SimpleSAML/Auth/SourceTest.php

tests/lib/SimpleSAML/Auth/StateTest.php

tests/lib/SimpleSAML/ConfigurationTest.php

tests/lib/SimpleSAML/DatabaseTest.php

tests/lib/SimpleSAML/Locale/LanguageTest.php

tests/lib/SimpleSAML/Locale/LocalizationTest.php

tests/lib/SimpleSAML/Locale/TranslateTest.php

tests/lib/SimpleSAML/Metadata/MetaDataStorageHandlerTest.php

tests/lib/SimpleSAML/Metadata/MetaDataStorageSourceTest.php

tests/lib/SimpleSAML/Metadata/SAMLBuilderTest.php

tests/lib/SimpleSAML/Metadata/SAMLParserTest.php

tests/lib/SimpleSAML/ModuleTest.php

tests/lib/SimpleSAML/SessionHandlerPHPTest.php