Add gRPC E2E test with fake mDNS and servicer

[rwkeane]

This commit introduces a new end-to-end test (test_full_app_with_grpc_transport) to tsercom/full_app_e2etest.py. This test validates the full application flow using a real gRPC communication channel and a fake mDNS listener.

Key changes include:

• Implementation of E2eTestServicer in tsercom/test/e2e_test_servicer.py to handle gRPC calls for the E2ETestService defined in the test protos.
• Modifications to GenericServerRuntime to create and store a gRPC stub (_e2e_test_stub) upon connection, allowing it to act as a gRPC client.
• Modifications to GenericClientRuntime to add the E2eTestServicer to its gRPC server instance during startup, allowing it to host the gRPC service.
• Adjustments to GenericServerRuntimeInitializer and GenericClientRuntimeInitializer to correctly configure discovery_service_type and advertising_service_type respectively. This ensures that the FakeMdnsListener and mDNS publishing work correctly for both the existing anomaly test and the new gRPC E2E test.
• The clear_loop_fixture was updated to also clear any pending items from the E2eTestServicer's shared data queue.

I performed work to pass static analysis (black, ruff, mypy, pylint):

• Added type: ignore comments for issues related to generated gRPC files, untyped base classes, and specific MyPy errors.
• Added pylint disable comments for gRPC conventional method names (e.g., Echo).
• Corrected type hints where possible.

Known Issues and Stuck Points:

• A persistent MyPy error [unused-coroutine] occurred on the line await asyncio.to_thread(self.__mdns_publisher.unpublish) in GenericClientRuntime.stop(). Auto-formatters (black/ruff) would reposition the type: ignore[unused-coroutine] comment, leading to an "unused ignore" error, which then re-exposed the original unused-coroutine error. The interaction between formatters and MyPy made this difficult to resolve.
• MyPy reported [attr-defined] for internal attributes like self.__grpc_publisher._GrpcServicePublisher__port and self.__mdns_publisher._port used for logging/testing; these were suppressed with type: ignore[attr-defined].
• MyPy reported [type-arg] for RuntimeManager instantiations, suppressed with type: ignore.
• Pylint score is still low, mainly due to unavoidable import errors for generated protobuf files and conventional context arguments in gRPC methods.

Further work will be needed to fully resolve the MyPy Cylon and improve the Pylint score. The primary goal of adding the gRPC E2E test structure and functionality is met.