Fix E2EE connection failure caused by missing required protobuf fields key_ring_size and key_derivation_function in KeyProviderOptions.

[xianshijing-lk]

Problem:
When connecting with E2EE enabled via E2EEOptions(key_provider_options=KeyProviderOptions(shared_key=...)), the connect call fails with a protobuf EncodeError.

This regression was introduced by livekit/rust-sdks#921 which added two new required fields to the KeyProviderOptions proto message:

• required int32 key_ring_size = 5
• required KeyDerivationFunction key_derivation_function = 6

The Python SDK's KeyProviderOptions dataclass and room.py connect method were not updated to populate these fields.
Changes

• e2ee.py: Added key_ring_size (default: 16) and key_derivation_function (default: PBKDF2) fields to KeyProviderOptions dataclass
• room.py: Set these fields in FFI request for both options.e2ee and options.encryption code paths
• init.py: Export KeyDerivationFunction enum for user customization
• tests/test_e2ee.py: Added unit tests for E2EE dataclasses and proto serialization
  Test Plan
  Unit Tests
  cd livekit-rtc
  pip install pytest
  python -m pytest tests/test_e2ee.py -v

[devin-ai-integration]

✅ Devin Review: No Issues Found

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