branch-3.1: [chore](cloud) Expose download command in tools/fdb/fdb_ctl.sh for convenience #58257 (#58263)

Cherry-picked from #58257

Co-authored-by: Gavin Chou <gavin@selectdb.com>

Author: github-actions[bot]

tools/fdb/fdb_ctl.sh

@@ -36,7 +36,7 @@ else
 fi
 
 if [[ ! -d "${FDB_HOME}" ]]; then
-    echo "Please set and create FDB_HOME first"
+    echo "Please set and create FDB_HOME:${FDB_HOME} first"
     exit 1
 fi
 
@@ -511,6 +511,9 @@ fdbcli)
 config)
     generate_regression_config true
     ;;
+download)
+    download_fdb
+    ;;
 *)
     unknown_cmd "${cmd}"
     ;;