How do I embed an "EVA" view display in a twig template?
EVAs get added as a field with name like VIEW_ID_DISPLAY_ID. They should appear in the content variable like any other field.

If you've added your EVA to the node's display you should be able to render your EVA, with the configuration from the Manage Display screen, like 

{{ content.contenu_relation_groupe_entity_view_1 }}.