function ownerHasEngine(owner, engineName) {
  return owner.hasRegistration(`engine:${engineName}`);
}
Checks the owner to see if it has a registration for an Engine. This is a
proxy to tell if an Engine's assets are loaded or not.

@see https://github.com/ember-engines/ember-engines/blob/8f66b5e3b8089cd53884be49f270cac05f9a3d17/addon/-private/router-ext.js#L152-L164

@param {Owner} owner
@param {String} name
@return {Boolean}