Add exhaustive subgraph quantum volume measurement.

[kylegulshen]

Description

There was an offline request for a more optimized measurement of quantum volume that measures each subgraph of a particular lattice. I have added a method that performs this measurement and reports the probability and lower bound for the list of induced subgraphs, which can be attained by a separate helper function.

Checklist

• The above description motivates these changes.
• There is a unit test that covers these changes.
• The code respects the API separation discussed in .github/CONTRIBUTING.md.
• Relevant references and equations are cited using our standard reference style.
• All new and existing tests pass locally and on Semaphore.
• Parameters have type hints with PEP 484 syntax.
• Functions and classes have useful sphinx-style docstrings.
• (New Feature) The docs and example notebooks have been updated accordingly.
• The changelog (docs/source/changes.rst) has a description of this change.