Issue #3477573 by pdureau, grimreaper: Better stories slots processing

.cspell-project-words.txt

.../ui_patterns_legacy/src/Element/ComponentElementAlter.php

modules/ui_patterns_legacy/ui_patterns_legacy.info.yml

modules/ui_patterns_legacy/ui_patterns_legacy.services.yml

...ui_patterns_library/src/Element/ComponentElementAlter.php

modules/ui_patterns_library/src/StoriesSyntaxConverter.php

...ns_library/tests/src/Unit/StoriesSyntaxConversionTest.php

modules/ui_patterns_library/ui_patterns_library.services.yml

src/Element/ComponentElementAlter.php

.../PropTypeNormalization/LinksPropTypeNormalizationTest.php