Add batched exponential for inhomogeneous term
Added support for the inhomogeneous term in the batched versions of Lanczos and Taylor methods. The choice of adding the inhomogeneous term is now done through an optional argument of exponential_apply_batch instead of querying the hamiltonian. Added and improved tests for these new features.
Add batched exponential for inhomogeneous term.
- I have checked that my code follows the Octopus coding standards
- I have added tests for all the new features added in this request.