Share auto-hang-up lifecycle across telephony serializers

[mr-meetpatel]

Summary

• Adds AutoHangupFrameSerializer to share terminal-frame handling across REST-based telephony serializers
• Migrates Twilio, Telnyx, and Plivo while preserving their provider-specific hang-up behavior
• Prevents repeated or concurrent EndFrame and CancelFrame processing from triggering duplicate hang-up attempts
• Leaves Genesys, Exotel, Vonage, and non-telephony serializers unchanged

Testing

• Added lifecycle tests covering terminal-frame detection, disabled handling, duplicate attempts, concurrency, and provider errors
• Added regression coverage for Twilio, Telnyx, and Plivo
• Verified Genesys and Protobuf serializer behavior remains unchanged
• Ran 59 focused tests, Ruff lint, and Ruff formatting checks

Fixes

• Fixes Introduce a Reusable Auto-Hang-Up Lifecycle for REST-Based Telephony Serializers #5013