WIP: Run more of dEQP in the CI and use softpipe

This series reworks the use of a software renderer (softpipe) in the gitlab CI. The selected tests cover parts of dEQP 2, 3, and 31 and are all passing as of this merge request.

Softpipe was selected because it already supports GLES 3.1, and the runtime for the workload required by dEQP (many shaders only run once) is actually lower then with llvmpipe as a host driver.

WIP: The test set contains tests that flip