feat: detect unused snapshots despite xdist

[epenet]

Description

Improve xdist compatibility - with the ability to serialize/deserialize the report data.
See home-assistant/core#128162 for sample implementation

Related Issues

Known Limitations
pytest-xdist support only partially exists. There is no issue when it comes to reads however when you attempt to run pytest --snapshot-update, if running with more than 1 process, the ability to detect unused snapshots is disabled. See #535 for more information.
We welcome contributions to patch these known limitations.

Checklist

• This PR has sufficient documentation.
• This PR has sufficient test coverage.
• This PR title satisfies semantic convention.

Additional Comments

No additional comments.

[codecov]

Codecov Report

Attention: Patch coverage is 87.09677% with 8 lines in your changes missing coverage. Please review.

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- Coverage   97.74%   97.34%   -0.40%     
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  Files          21       21              
  Lines        1596     1658      +62     
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+ Hits         1560     1614      +54     
- Misses         36       44       +8     

[epenet]

After running successfully on Home Assistant - it was decided to revert it because serialization/de-serialization of the report was taking too long.
We may need to add an option so it only takes effect if --snapshot-update or --snapshot-details is set
Or maybe add a new settting --snapshot-xdist-report
See home-assistant/core#129311