Virtual distilation error mitigation main function UvA project

[Jegbrz]

This pull request implements the main function (execute_with_vd) for the virtual distillation error mittigation scheme. The function accepts executors that return a density matrix (simulated) or a list of measurement bitstrings.

Right now only the Z observable is supported.

• I license this contribution under the terms of the GNU GPL, version 3 and grant Unitary Fund the right to provide additional permissions as described in section 7 of the GNU GPL, version 3.

Before opening the PR, please ensure you have completed the following where appropriate.

• I added unit tests for new code.
• I used type hints in function signatures.
• I used Google-style docstrings for functions.
• I updated the documentation where relevant.
• Added myself / the copyright holder to the AUTHORS file

[github-actions]

Hello @Jegbrz, thank you for submitting a PR to Mitiq! We will respond as soon as possible, and if you have any questions in the meantime, you can ask us on the Unitary Fund Discord.

[codecov]

Codecov Report

Attention: Patch coverage is 24.56140% with 86 lines in your changes missing coverage. Please review.

Project coverage is 96.79%. Comparing base (7b5f549) to head (7dabe9a).

Files with missing lines	Patch %	Lines
mitiq/vd/vd.py	14.70%	58 Missing ⚠️
mitiq/vd/vd_utils.py	37.77%	28 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2658      +/-   ##
==========================================
- Coverage   98.74%   96.79%   -1.96%     
==========================================
  Files          93       95       +2     
  Lines        4219     4332     +113     
==========================================
+ Hits         4166     4193      +27     
- Misses         53      139      +86     

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