test: harden Docker release smoke probes

scripts/lib/docker-e2e-logs.sh

@@ -31,6 +31,34 @@ run_logged_print() {
   rm -f "$log_file"
 }
 
+run_logged_print_heartbeat() {
+  local label="$1"
+  local interval_seconds="$2"
+  shift 2
+  local log_file
+  log_file="$(docker_e2e_run_log "$label")"
+  "$@" >"$log_file" 2>&1 &
+  local command_pid=$!
+  local started_at
+  started_at="$(date +%s)"
+  local status=0
+  while kill -0 "$command_pid" 2>/dev/null; do
+    sleep "$interval_seconds"
+    if kill -0 "$command_pid" 2>/dev/null; then
+      local now
+      now="$(date +%s)"
+      echo "still running $label ($((now - started_at))s elapsed)"
+    fi
+  done
+  set +e
+  wait "$command_pid"
+  status=$?
+  set -e
+  docker_e2e_print_log "$log_file"
+  rm -f "$log_file"
+  return "$status"
+}
+
 docker_e2e_run_log() {
   local label="$1"
   local tmp_dir="${TMPDIR:-/tmp}"