[VOQ][saidump] To move saidump.sh from the sonic-buildimage repo to the sairedis repo (#1298)

To fix the issue: sonic-net/sonic-buildimage#13561
The existing saidump use https://github.com/sonic-net/sonic-swss-common/blob/master/common/table_dump.lua script which loops the ASIC_DB more than 5 seconds and blocks other processes access.

This solution uses the Redis SAVE command to save the snapshot of DB each time and recover later, instead of looping through each entry in the table.

Author: JunhongMao

syncd/scripts/saidump.sh

@@ -0,0 +1,39 @@
+#!/bin/bash
+set -e
+
+save_saidump_by_rdb()
+{
+  local filepath="/var/run/redis/sonic-db/database_config.json"
+
+  # Get hostname, port, redis directory
+  local redis_config=$(python3 -c "
+import json
+with open('$filepath') as json_file:
+  data = json.load(json_file)
+  print(data['INSTANCES']['redis']['hostname'], data['INSTANCES']['redis']['port'], data['INSTANCES']['redis']['unix_socket_path'])")
+
+  # split
+  redis_config=(${redis_config// / })
+  local hostname=${redis_config[0]}
+  local port=${redis_config[1]}
+  local redis_dir=`dirname ${redis_config[2]}`
+  logger "saidump.sh: hostname:$hostname, port:$port, redis_dir:$redis_dir"
+
+  logger "saidump.sh: [1] Config Redis consistency directory."
+  redis-cli -h $hostname -p $port CONFIG SET dir $redis_dir > /dev/null
+
+  logger "saidump.sh: [2] SAVE."
+  redis-cli -h $hostname -p $port SAVE > /dev/null
+
+  logger "saidump.sh: [3] Run rdb command to convert the dump files into JSON files."
+  rdb --command json  $redis_dir/dump.rdb | tee $redis_dir/dump.json > /dev/null
+
+  logger "saidump.sh: [4] Run saidump -r to update the JSON files' format as same as the saidump before. Then we can get the saidump's result in standard output."
+  saidump -r $redis_dir/dump.json -m 100
+
+  logger "saidump.sh: [5] Clear the temporary files."
+  rm -f $redis_dir/dump.rdb
+  rm -f $redis_dir/dump.json
+}
+
+save_saidump_by_rdb