Fix scrubbing mode's intermittent seek prevention for image rendering

Scrubbing mode includes a feature to prevent new seek operations from being processed until the current operation finishes. This feature relies on the VideoFrameMetadataListener to ascertain when a seek completes to unblock the queue. This mechanism was broken for image playback because a similar listener did not exist.

With this in mind this CL adds an ImageMetadataListener class that can be used to identify when image seeks complete.

Issue: androidx/media#2815
PiperOrigin-RevId: 907524940
(cherry picked from commit d572508ac3f517a742ff9e74565e8113d8fcbd8c)