OpenGL: add support for flipping and test orientation + smoke test

The current code is now able to rotate depending on the filters engine orientation coming from the OpenGL provider, but it wasn't able to flip yet. Because the orientation will rotate vertical flipping, only horizontal flipping is needed for any direction flipping.

This commit MR add support for those, and check that it's working correctly through offscreen OpenGL implementations, while smoke-testing the opengl filter.