Issue #3486547 by pdureau, just_like_good_vibes: add new EnumSetPropType

modules/ui_patterns_legacy/src/PropConverter.php

src/EnumTrait.php

src/Plugin/UiPatterns/PropType/EnumListPropType.php

src/Plugin/UiPatterns/PropType/EnumPropType.php

src/Plugin/UiPatterns/PropType/EnumSetPropType.php

src/Plugin/UiPatterns/Source/CheckboxesWidget.php

src/Plugin/UiPatterns/Source/SelectWidget.php

src/Plugin/UiPatterns/Source/SelectsWidget.php

src/PropTypePluginBase.php

src/SchemaManager/CompatibilityChecker.php