CI: Set up OpenGL driver support for automation

[bryphe]

Our Azure CI config doesn't support testing an OpenGL app out-of-the-box. It seems the machines are VMs w/o any hardware OpenGL support.

This is problematic for testing changes like #390 as well as a blocker for snapshot tests like #156 . Our unit tests today dance around this by not calling into any methods that use OpenGL resources.

We should set up our configs to be able to run OpenGL, though, so we can fully test the app in CI.

One tool to do this would be to leverage the Mesa3d software drivers. It might also need to be coupled with a virtual framebuffer tool like xfvb on Linux.

The fix is to properly configure our CI machines to support creating an OpenGL context.