refine register module

[sgrava]

Collection of register module issues:

• Deprecate Register.from_graph(). Getting the coordinates or the Register directly from the DataGraph is cleaner. Not really needed as long as we offer and present aternatives

• Graph → register labeling
  Asses how labels are handled? Is it coherent between graph and register? QoolQit register has to follow QoolQit labeling. It will be QoolQit responsibility to support conversion to Pulser labeling

  • networkx default label nodes as 0,1,2,3,4….. But in principle you can put whatever you want.
  • Pulser label atoms/nodes as “q0”, “q1”, “q2”, etc…

  Internally, each networkx node i becomes atom “q_i”, so order is preserved.

• Convenient methods for quick register creations.
  Same methods as DataGraph, which will change to only have edge weights, the register method ones will actually create coordinates.
  add register class methods #403

• Center register drawing

• Register.__init__ lacks validation
  add input validation to register default constructor #397
  validate input in register default constructor #398

• add interaction_matrix method
  add interaction_matrix method to Register #417
  add interaction matrix method to register #419

[sgrava]

Closing this leaving #403 open to be closed later.