When possible, the phase is not applied when computing the application of the…

Description

When possible, the phase is not applied when computing the application of the exponential of the Hamiltonian. In this case, only a phase correction is applied, after applying the periodic boundary conditions. The implementation need to be properly benchmarked.

News snippet

Optimization of the application of the phase for the Chebycev and Lanczos exponential methods.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.