Ensure CI/CD parity across platform providers

[56kyle]

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Overview

This pull request implements several changes to the CI/CD pipelines for GitHub, GitLab, and Bitbucket to ensure feature parity and consistency across these platforms.

Changes

• GitHub: Replaced placeholder Rust CI/CD with a fully implemented setup using nox sessions.
• GitLab: Updated pipeline to include tests for Windows and macOS, added additional cache key options, and ensured feature parity with other providers.
• Bitbucket: Added Windows and macOS tests, configured uploads to TestPyPI, and introduced caching based on file changes. Lint and format commands were condensed and updated to align with other platforms.
• Unified CI/CD configurations by condensing and combining styling commands in nox sessions.
• Updated generated project templates and documentation to align with new cookiecutter values and other CI/CD adjustments (e.g., URLs, CONTRIBUTING.md updates, etc.).
• Added proofs of concept for Bitbucket and GitLab CI/CD configurations.

Notes

• Several redundant or platform-specific configurations have been optimized or removed to enhance maintainability.
• Documentation was updated to reflect new processes and project structure.