refactor: [FC-0072] migrate project to swift 6

[IvanStepanok]

This commit updates the entire project to Swift 6, incorporating language features like Sendable conformance and improved concurrency support. Key changes include:

• Sendable conformance added across the codebase for thread safety.
• Extensive migration to async/await for modern concurrency handling.
• New SwiftGen rule introduced to ensure compatibility with Swift 6.
• Significant updates to the test suite:
  • Most tests refactored and optimized for reliability and faster execution.
  • Enhanced compatibility with CI/CD pipelines.

BREAKING CHANGE: The project now requires Swift 6, and dependencies or integrations using earlier Swift versions may need adjustments to ensure compatibility.

[openedx-webhooks]

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[IvanStepanok]

@rnr Thanks for reviewing! All feedback are addressed

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