SDK / exoplayer

- Increase the search window size to fix TS seeking for problematic
  media we've had provided to us.
- As per my comments on the issue, we should look at doing more here
  to better fix the problem. This will solve the worst of the
  immediate problem, however.
- The memory usage is non-trivial, particularly with the increased
  search window size. I've made the allocations only live whilst
  determining duration and seeking to address this. I've done the same
  for PS just for consistency.

Issue: #5097

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=221449988