This PR includes the Python server and client code to reproduce the ping timeout issue that was recently reported by Dataflow as well as in issue #38282. This PR is only meant for reference and doesn't require to be merged to the repo.

Steps to reproduce the ping timeout via Bazel in Python:

• export GRPC_TRACE=tcp,http,http2_keepalive,http2_ping,polling,polling_api
• export GRPC_VERBOSITY=debug
• Run bazel run //examples/python/ping_timeout_repro:greeter_server_py --copt=-DGRPC_DO_NOT_INSTANTIATE_POSIX_POLLER to start the Python server
• Run bazel run //examples/python/ping_timeout_repro:repro_greeter_client_py --copt=-DGRPC_DO_NOT_INSTANTIATE_POSIX_POLLER to start the Python client

Steps to reproduce the ping timeout directly using Python without Bazel:

• Use a grpcio version >=1.68.0
• export GRPC_TRACE=tcp,http,http2_keepalive,http2_ping,polling,polling_api
• export GRPC_VERBOSITY=debug
• Run python examples/python/ping_timeout_repro/greeter_server.py to start the Python server
• Run examples/python/ping_timeout_repro/repro_greeter_client.py to start the Python client

NOTE: The issue can only be reproduced via Bazel when including the --copt flag via command line, however if running directly via Python it doesn't require the command-line flag. Running the example as described above with the specific debug trace logs should show log lines such as:

I0000 00:00:1745420380.475681 3473830 chttp2_transport.cc:1963] ipv6:%5B::1%5D:50051: Ping timeout. Closing transport.
...
I0000 00:00:1745420380.476151 3473830 chttp2_transport.cc:1844] 0x7ffb90001600 CANCEL PINGS: UNKNOWN:ping timeout {grpc_status:14}
...
I0000 00:00:1745420380.477078 3473830 chttp2_transport.cc:1844] 0x7ffb90001600 CANCEL PINGS: UNKNOWN:goaway sent
...
I0000 00:00:1745420380.477298 3473830 ev_posix.cc:186] (polling-api) fd_shutdown(5)
...
I0000 00:00:1745420380.477517 3473830 tcp_posix.cc:1105] TCP:0x55a33ded8300 got_read: UNKNOWN:FD Shutdown {children:[UNAVAILABLE:endpoint shutdown]}