Restore gwinc TCS calculation
A calculation of the TCS efficiency required to achieve a given SRC loss is described in the comments of our ifo.yaml files. But at some point the implementation was removed from pygwinc. TCS can be an important consideration, so we should put this back in.
We should check it for correctness, and I think it will need updating to scale with material parameters, and integrate with the new quantum code once that is merged.