Add full TLS support for Python gRPC runtime and documentation

[akeshai]

Why are these changes needed?

Distributed AutoGen nodes currently communicate over insecure gRPC channels. This PR adds support for full TLS (Transport Layer Security) between nodes, enabling secure and encrypted communication in production environments.

Related issue number

Fixes #4373

Description

This PR implements TLS support in the Python gRPC runtime and provides the necessary infrastructure and documentation for secure deployment.

Key Changes:

• Python Runtime: Updated GrpcWorkerAgentRuntimeHost and GrpcWorkerAgentRuntime to accept and utilize gRPC server and channel credentials.
• Documentation: Added a new user guide distributed-deployment-tls.md covering certificate generation and configuration for both Python and .NET interoperability.
• Infrastructure: Added infra/autogen-tls.bicep as a reference for secure Azure Container Apps deployment with Key Vault integration.
• Testing: Added a comprehensive test suite test_worker_runtime_tls.py verifying secure communication and credential validation.

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/.
• I've added tests corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed (Ran ruff/mypy and automated TLS tests locally).

[akeshai]

@microsoft-github-policy-service agree