This information isn't easily available to the player at the moment (or it
would need to revaluate this every time), so add it to MediaPeriodInfo similar
to the existing isLastInTimelinePeriod.
The player needs to know whether a MediaPeriod is the last in its Timeline
window if we want to add an option to pause at the end of a window.
PiperOrigin-RevId: 294877628
714fa477d0