The idea was to not even write any samples to SampleQueues as
they are not needed during the metadata extraction process.
However, this is not easily possible as long as we use our
existing Extractors and MediaSource/Periods for loading given
how deeply ingrained the extraction of samples is in these
classes. For most common formats like MP4, no samples will be
extracted anyway as they can finish the prepare step without
reading any samples.
PiperOrigin-RevId: 650529371
2bb719fd54