Share OpenGL context between multiple instances of Webots

[lukicdarkoo]

In order to parallelize the execution of multiple simulations, we can either create multiple environments within a single Webots instance or run multiple instances of Webots.

Our initial tests show that creating multiple environments within a single Webots instance suffer from a low CPU utilization as steps a synchronized simulation wide. Running multiple instances of Webots is limited by VRAM as things like textures and meshes are not shared between Webots instances.

We need a more effective way to parallelize the execution of multiple simulations. One approach would be to reuse textures and meshes between multiple Webots instances.