Add option to quantize time to whole frames of framerate.

This ensures that only whole frames are displayed. Good for ensuring the frames you see in the editor are what is shown at runtime and for creating more stop-motion like effects efficiently.

![CleanShot 2023-07-13 at 15 36 21@2x](https://github.com/rive-app/rive/assets/454182/c796c493-c359-469e-b5f4-8dd37686e7b7)

Diffs=
8b49fcbc5 Add option to quantize time to whole frames of framerate. (#5578)