Derivatives of QHBM expectation with respect to classical model parameters

[zaqqwerty]

The calculation of the VQT derivative is actually more general. This issue is to implement the classical model parameter derivative equation from the appendix.

[zaqqwerty]

All that's left here is to add derivative tests. Should include the following cases:

• energy and circuit have variables in common
• energy has multiple variables of different shapes, for example when energy is an MLP