Missing og_audience field reference causes fatal errors in og_menu_entity_delete() during entity deletion

Thanks for creating the issue @franceslui. When we looked at this together this afternoon, it appears this field is only used here, and nowhere else outside of tests. I believe, but could be wrong (will check with @claudiu.cristea), that the intent is for this to be field name agnostic, though a field is indeed expected.

My gut is saying use \Drupal\og\OgGroupAudienceHelper::getAllGroupAudienceFields:
https://git.drupalcode.org/project/og/blob/404bb45bd8849cca32f34e5a78c4f...
and get all the fields.

The only question this solution brings up is that this module should likely install a default as, og when group content is being created, or maybe it does and we deleted it, but from looking at the code it didn't seem to be the case...

Oh while getting the issue ready to add this loop through fields... I see that the field will get created automatically on the first og menu that gets created...

Still needs fixing, but mitigated by finishing the config