…aidump_by_route_size (sonic-net#2972)

* * [saidump]
•	Saidump for DNX-SAI sonic-net/sonic-buildimage#13561

Solution and modification:
To use the redis-db SAVE option to save the snapshot of DB each time and recover later, instead of looping through each entry in the table and saving it.

(1) Updated sonic-buildimage/build_debian.sh, to install Python library rdbtools into the host.
(2) Updated sonic-buildimage/src/sonic-sairedis/saidump/saidump.cpp, add a new option -r, which updates the rdbtools's output-JSON files' format.
(3) Add a new script file: files/scripts/saidump.sh, to do the below steps
  For each ASIC0, such as ASIC0,

  #1. Save the Redis data.
  sudo sonic-db-cli -n asic$1 SAVE > /dev/null

  #2. Move dump files to /var/run/redisX/
  docker exec database$1 sh -c "mv /var/lib/redis/dump.rdb /var/run/redis$1/"

  #3. Run rdb command to convert the dump files into JSON files
  sudo python /usr/local/bin/rdb --command json  /var/run/redis$1/dump.rdb | sudo tee /var/run/redis$1/dump.json > /dev/null

  #4. Run saidump -r to update the JSON files' format as same as the saidump before. Then we can get the saidump result in standard output.
  docker exec syncd$1 sh -c "saidump -r /var/run/redis$1/dump.json"

  #5. clear
  sudo rm -f /var/run/redis$1/dump.rdb
  sudo rm -f /var/run/redis$1/dump.json

(4) Update sonic-buildimage/src/sonic-utilities/scripts/generate_dump, replace saidump with saidump.sh
* * [saidump]
•	Saidump for DNX-SAI sonic-net/sonic-buildimage#13561