webgl test | switch to glesbinding based node module when available

with the next release of [glbinding](https://github.com/cginternals/glbinding) gles and webgl interfaces will be exposed and a npm package for headless webgl is planned that can be used for testing webgl in a headless renvironment.

The issue names no files, tests, or entry points. Check the current WebGL testing setup and whether the planned glbinding npm package is available; identify where the headless test module would be selected. Done means using the GLES-based Node module for WebGL tests when it is available.

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