Enable Swift 6 Language Mode

This PR updates Swinject to fully embrace Swift 6.0 and modern Swift concurrency patterns. The changes include both tooling updates and code modernization to leverage Swift 6's features.

It still requires some more profound changes if we want to adopt Swift Concurrency fully, but it seems the case since we want to prioritize performance over using the latest features. In the majority of cases, using an actor or Mutex from the Synchronization framework is twice as slow as using the traditional lock/Fair Lock mechanisms.

Key Changes

Tooling Updates

• Updated Swift tools version to 6.0.0
• Updated SwiftFormat configuration to target Swift 6.0

Code Modernization

• Replaced custom logging system with environment variable-based logging (SWINJECT_LOGGING_ENABLED)
• Enhanced thread safety by adopting modern Swift concurrency:
  • Converted ThreadSafeDictionary from lock-based to actor-based implementation
  • Added Sendable conformance to key types
• Improved code organization:
  • Consolidated ObjectScope definitions into a single file
  • Removed redundant ReadWriteLock implementation in favor of actor-based concurrency
  • Made ObjectScope a final class and marked it as @unchecked Sendable

Migration Notes

• If you were using the custom logging function, switch to using the SWINJECT_LOGGING_ENABLED=1 environment variable
• Code using ThreadSafeDictionary may need to be updated to handle the actor-based implementation
• The changes maintain API compatibility while improving thread safety and performance

Testing

Please ensure to test thoroughly, especially in concurrent scenarios, as this update includes significant changes to thread safety mechanisms.