Save initial onsite values for potential performance improvement.

The potential performance improvement may come from cythonised dict<int> lookup
vs pure pythong function call of the Hamiltonian value.

Further performance improvement can be made by making tinyarray cimport-able
and use libcpp.map instead of dict when saving static onsite values.
3 jobs for master in 5 minutes and 19 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build:package #145469

00:00:55

 
  Test
passed build:documentation #145471

00:04:23

passed test:package #145470

00:01:01