Use pyquil symmetrization functionality

[kylegulshen]

Description

We moved and expanded the symmetrization functionality from observable_estimation over to pyquil. This PR makes use of the pyquil functionality. Calibration hasn't yet been made to work with all options of symmetrization. A warning is thrown if the weight of a calibrated observable is greater than the symmetrization strength (symm_type).

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.
• (Bugfix) The associated issue is referenced above using
  auto-close keywords.
• The changelog (docs/source/changes.rst) has a description of this change.

[joshcombes]

It is much easier to under stand and shorter now that symmetrization is in pyquil.

[joshcombes]

One possibility is to use exhaustive if weight > strength of current sym_type.

Realistically the stabilizers are usually weight 4, for codes people care about. (This suggests, as a separate pyQuil PR, that we might consider trying to find a family of strength 4 OAs.) In general but you might find some use in up to weight 6.

[karalekas]

Nice! Happy we're deduping. Will approve when tests pass.