REL-1914: Added flip transformation to GMOS OIWFS when using Altair.

My first pull request!
The task was to flip the GMOS OIWFS FOV when using Altair. There is one part of my solution that leaves me a bit unsatisfied. That is that I created a AffineTransform (called altairTransform) to apply the flip. If the LGS+OIWFS mode is used for other instruments in the future, they will also need this transformation. I thought of making altairTransform accessible to other instruments OIWFS classes, but I didn't know where to put it.