The deterministic_select! macro waits on multiple async operations simultaneously,
returning when one of them completes. Branch ordering is determined by GlobalRng
for deterministic but fair selection.
Enable the #4549 fast-exit behaviour: a fatal (non-graceful) network event
listener exit will abort the process with [FATAL_LISTENER_EXIT_CODE] for a
prompt service-manager restart, rather than risk hanging in teardown. Call once
from the production node entry point. See [ABORT_ON_FATAL_LISTENER_EXIT].
Opt in to the distinct [FAST_CRASH_EXIT_CODE] for fast boot-crashes (#4551).
Call ONLY from the production node entry point, and ONLY after confirming the
supervising systemd unit advertises support for exit 45 (see the entry point’s
marker check). See [EMIT_FAST_CRASH_EXIT_CODE].