feat: Implement Fixed timestep

[eonarheim]

===:clipboard: PR Checklist :clipboard:===

• 📌 issue exists in github for these changes
• 🔬 existing tests still pass
• 🙈 code conforms to the style guide
• 📐 new tests written and passing / old tests updated with new scenario(s)
• 📄 changelog entry added (or not needed)

==================

v0.27.0 Milestone related,

This PR adds the ability to configure a fixed FPS for the update loop. One advantage of setting a fix update is that you will have a more consistent and predictable physics simulation. Excalibur graphics will be interpolated automatically to avoid any jitter in the fixed update.

• If the fixed update FPS is greater than the display FPS, excalibur will run multiple updates in a row (at the configured update elapsed) to catch up, for example there could be X updates and 1 draw each clock step.
• If the fixed update FPS is less than the display FPS, excalibur will skip updates until it meets the desired FPS, for example there could be no update for 1 draw each clock step.

const game = new ex.Engine({
  fixedUpdateFps: 20 // 20 fps fixed update, or a fixed update delta of 50 milliseconds
});

The graphics interpolation can be turned off on a per body basis.

// turn off interpolation on a per actor basis
const actor = new ex.Actor({...});
actor.body.enableFixedUpdateInterpolate = false;

Fixed update @ 10 fps - graphics without interpolation

Fixed update @ 10 fps - graphics with interpolation

TODOs:

• Interpolate graphics to prevent jitter
• Convenient way to set in constructor
• Tests