Improve per-frame position saving

[kjack9]

Positions are currently added to the cache if the player has moved at least rewindMinDistanceChangeToSavePosition world units since the last saved position. However, if the player is moving fast and has moved say 2x that distance, only one position is added to the cache.

The result is that if a player is going fast enough, they can go farther into an out-of-bounds area than if they were going slowly.

Implement a system that accounts for this difference, and consistently rewinds the player at the same point regardless of speed.