Fix EZP-22180: loading (reverse) relations does not check for published Content

This PR resolves https://jira.ez.no/browse/EZP-22180

In Legacy Storage Content gateway methods loadRelations() and loadReverseRelations() did not limit the result to the published Content. Only loadReverseRelations() limited the related Content to the current version.

This was not sufficient and resulted in incorrect data returned in two cases:

1. when Content is in ARCHIVED state
1. when Content has only first (unpublished) draft

This fixes the issue and adds missing integration tests.