Improve quick scrub auto-advance

- Explicitly list thresholds, including for auto-advance
- Thresholds for auto-advance are smaller, so you only reach them if
  you scroll to the edges of the track
- Because auto-advance is it's own section, removed longer initial
  auto-advance delay
- When moving out of auto-advance, stay on the same page instead of
  jumping back

Bug: 70180755
Change-Id: I4a8926f9ca944ee619cc71a77b893be894248458