Improve messages of QGTJacobian user-errors
Created by: PhilipVinc
This PR does:
- Improve the readability of the message introduced a while back explaining that you can't multiply the real part of a QGT with a complex vector
- Improves the readability of the message thrown by
QGT
when you multiply the qgt by a pytree with the wrong shape - Adds this input validation logic to
QGTJacobianDense
as well