MNT: Refactor Parallel MonteCarlo and Stochastic Seeding

[phmbressan]

Pull request type

• [X] Code maintenance (refactoring, formatting, tests)

Checklist

• [ ] Tests for the changes have been added (if needed)
• [ ] Docs have been reviewed and added / updated
• [X] Lint (black rocketpy/ tests/) has passed locally
• [X] All tests (pytest tests -m slow --runslow) have passed locally
• [ ] CHANGELOG.md has been updated (if relevant)

Current behavior

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New behavior

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Breaking change

• [ ] Yes
• [X] No

Additional information

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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 29.26829% with 87 lines in your changes missing coverage. Please review.

Project coverage is 74.93%. Comparing base (049276d) to head (26f692e).

Files	Patch %	Lines
rocketpy/simulation/monte_carlo.py	21.62%	87 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## enh/parallel_montecarlo #649 +/- ## =========================================================== + Coverage 74.16% 74.93% +0.77% =========================================================== Files 81 81 Lines 10080 9976 -104 =========================================================== Hits 7476 7476 + Misses 2604 2500 -104 ```

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