Improved performance of simulation

[leocus]

I reduced the time required for the simulation by using vertex_lists in pyglet

[pzhokhov]

very cool, thanks! I allowed myself some style changes to match the updated style upstream.
@leocus could you share some numbers about the performance change?
@olegklimov any chance you could take a look and see if the changes make sense to you? I don't know gl well enough to judge that.

[olegklimov]

time required for the simulation

That's cool! How much the render time has improved?

[leocus]

On my setup (i5-8250U, 16GB RAM DDR4) i measured those times (over 100 simulations):

• Original version:
  • Mean: 8.92 s/simulation
  • Std: 0.59 s/simulation
• This pull request:
  • Mean: 3.84 s/simulation
  • Std: 0.25 s/simulation

[xeviknal]

This PR introduced this nasty memory leak: #2062
A community member created a PR to approach this: #2096

Nice enhancement btw!

[leocus]

Sorry about that, glad it has been fixed :)