`ENETUNREACH` is semantically equivalent to `EHOSTUNREACH` (which is
already in `_NO_RETRY_ERRORS`) — both indicate the destination cannot be
reached at the network layer. Retrying immediately will not resolve the
condition.
In containerized environments (e.g., Home Assistant running in Docker
with bridge networking), a single ICMP "Network unreachable" response
can temporarily poison the container's routing cache. The unnecessary
retries reinforce the poisoned cache entry, causing cascading failures
for other devices on the same subnet.
* Transport tests under tests/transports/
* Protocol tests under tests/protocols/
* IOT tests under iot/
* Plus some minor cleanups, most code changes are related to splitting
up smart & iot tests
