CliffordOperator constructor from PauliOperator

[sagnikpal2004]

This pull request adds support for constructing a CliffordOperator directly from a PauliOperator. It also introduces corresponding tests to ensure the correctness of the new constructor.

Changelog

• Added a constructor to CliffordOperator that creates a Clifford operator from a PauliOperator
• Added an @inline getter for the phases field of a CliffordOperator.

Testing

• Added a test set to verify that applying a Pauli operator via the new constructor produces the same result as applying the Pauli operator directly.

Notes

• This consrtuctor is required to test apply_right #561, however it may not have any other practical uses, since any applications of PauliOperators can be done directly. Need advice if this should simply be left in the test file, or incorporated into the library
• A PauliOperator constructor from a CliffordOperator is also possible, and I can create a PR for it if deemed valueable for the library.

• The code is properly formatted and commented.
• Substantial new functionality is documented within the docs.
• All new functionality is tested.
• All of the automated tests on github pass.

Dependency of #561

[Krastanov]

could you make the small change to the tests for legibility

could you add a mention of this to the changelog

otherwise looks good for merge

of course, only after all tests pass

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.30%. Comparing base (ef85411) to head (85b698b).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #573      +/-   ##
==========================================
+ Coverage   84.27%   84.30%   +0.02%     
==========================================
  Files         108      108              
  Lines        6575     6581       +6     
==========================================
+ Hits         5541     5548       +7     
+ Misses       1034     1033       -1     

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[Fe-r-oz]

@sagnikpal2004, consider using squash merge for future PRs to maintain linear commit history. Currently, this PR's August 7 commit (ab41ecc) appears in the commit timeline before both August 8 merges from other PRs and its own August 10 merge (11165ae to 09f2172). Squash merging would resolve these timeline inconsistencies and provide clearer commit progression.

[sagnikpal2004]

@Fe-r-oz Thanks, I'll definitely keep that in mind next time!