Issue #3303321 by kristiaanvandeneynde: Drop 2.0.x upgrade path and update machine names

config/optional/views.view.group_members.yml

config/schema/group.views.schema.yml

group.views.inc

modules/gnode/config/optional/views.view.group_nodes.yml

src/Entity/Views/GroupRelationshipViewsData.php

src/Entity/Views/GroupViewsData.php

src/Plugin/views/relationship/GroupRelationshipToEntity.php

...ugin/views/relationship/GroupRelationshipToEntityBase.php

...n/views/relationship/GroupRelationshipToEntityReverse.php

src/Plugin/views/relationship/GroupToGroupRelationship.php

...s.view.test_group_relationship_to_entity_relationship.yml

...est_group_relationship_to_entity_reverse_relationship.yml

...ws.view.test_group_to_group_relationship_relationship.yml

...ernel/Views/GroupRelationshipToEntityRelationshipTest.php

...iews/GroupRelationshipToEntityReverseRelationshipTest.php

...Kernel/Views/GroupToGroupRelationshipRelationshipTest.php