Support thermal drift

[RaulPPelaez]

The library does not have utilities to compute the thermal drift. Should we add it to the interface somehow?
It could be:

• A new method added to the interface, similar to how we compute the noise
• A free standing function that works for any solver (like the Lanczos utility)
• A separate project altogether
  I am not sure what the cleanest thing is. To me adding it as a new method, like sqrtMdotW seems to make the most sense, but I fear the interface might become too complex at that point.