Draft: Fsc optimizations

Currently, I have modified the existing implementation by monkey patching in my changes as there is clear way to create a flag that says enable cupy. Unfortunately, this makes the code both clumsy and brittle. As it is currently implemented, I see no good way to make the changes I wish for as the Spinifel Settings, which decide if cupy can be used requires parameters not needed for FSC calculation. Also, running FSC calculations separately, as requested, is not a clean change either. I could again do it in the way I have made these changes if required.

The best way I think FSC should be handled is that it becomes a callable module, much like spinifel, with the option of running it in a headless mode for when we want to run it as part of our core iterations. Another way is that FSC starts depending on a configuration file for its parameters. This would be less intrusive at least for running it separately but running it as part of the core iteration would require us to add more parameters to spinifel settings to support FSC.