feat(flame_forge2d): Use a meter-to-pixels constant for rendering instead of zoom

[spydon]

What could be improved

We should be using a meter-to-pixels constant for rendering instead of using the zoom of the camera. The zoom is needed since there is a speed limit in Forge2D which we currently easily hit when we calculate one Forge2D unit as one pixel, instead of something larger.

Why should this be improved

To make the coding more natural, you shouldn't have to zoom in just to not hit the speed limit.

Any risks?

Yes, this will be a breaking change.

More information

https://www.iforce2d.net/b2dtut/gotchas#speedlimit