tweak(scrolling): Use smoothened frame rate to scale movement for scrolling and camera

[xezon]

• Fixes Frame time for scroll distance needs to be clamped #1657

This change uses smoothened frame rate to scale movement for scrolling and camera to avoid jumps on longer stalls.

TODO

• Update title
• Replicate in Generals

[helmutbuhler]

This creates an issue in this situation:

• Load a replay
• enable fast-forward
• disable fast-forward
• Move around with the camera. It will move slowly for a second or so.

[xezon]

Oh yes this happens because of the sudden change of average frame rate. Ok in that case we need a different solution.

[xezon]

I have appended a new solution that will floor the fps ratio at 5 fps to prevent big jumps on stalls.