Separating refresh rate from physics tick

[znichola]

The frame rate should not dictate the physics tick rate, it's not the 90s. To do this:

• [x] modify build script to allow custom flags for raylib build
• [x] implement the custom frame control without modifying the current functionality
• [x] implement a seperate timer for physics frame ticks and framerate, display them both on the overlay

[znichola]

This was semi solved here a67b0fa47f6102523ae725294d73ea3d037de53b but I'm not happy with how it was done, so idk about closing this. The implementation feels unfinished and how quite right. The issue is that when the timestep is too large, it's just not possible to keep smooth movement because the calculation time is long, and there is no way to jump the simulation forward, (it's derived, and can't be predicted, like you could with linear movement for instance.