Polish the gesture navigation tutorial sandbox

- Updated in-memory tutorial steps to a array so we can better track the tutorial progress after changing the theme.
- Added a 1.5 second delay for the gesture video when the user first starts a step, and when the app resumes.
- Updated the tutorial step indicator color: previous color was invisible against the background.

Bug: 188972959
Test: manual
Change-Id: Ia1a67f7cd9e7ed9802dbc0d88d1e3b432acfa127