Surround filter

[edyounis]

New features:

• Circuit.surround now can take a scoring function and a filter
  • The filter will prune the search space if provided
  • The scoring function can be used to change the scoring mechanism from the default gate count
  • The method is also now faster and more robust as it has been updated with the DAG methods
  • The starting point can now also be a region
• Circuit.next and Circuit.prev can now also take a CircuitRegion and return the next or prev points of the entire region
• Implemented CouplingGraph.is_linear

Bug Fixes:

• Fixed issues in circuit grid iteration with exclude=True
• Fixed Circuit.check_region missing bad regions where a gate would be half-in-half-out