Content after ad groups currently always resumes at the ad break position (unless
overridden by a seek or similar). In some cases, media inserting ads wants to
specify an offset after the ad group at which playback should resume. A common
example is a live stream that inserts an ad and then wants to continue streaming
at the current live edge.
Support this use case by allowing ad groups to specify a content resume offset
and making sure that the content start position after the ad group uses this offset.
PiperOrigin-RevId: 373393807
