add Rocksdb read 'cache keys shard bits' from the configuration file

Co-authored-by: Nliuzhen3 <liuzhen3@spdk01.cloud.bjpdc.qihoo.net>

- small-compaction-threshold
- max-cache-statistic-keys
Co-authored-by: Nrepls <bosen@staff.sina.com.cn>

issue:  https://github.com/OpenAtomFoundation/pika/issues/1152

fix: compile error with gcc 9.3 which is default in ubuntu 20.04

fix command info keyspace off

Use docker multi-stage build to reduce the docker image size

update the way to update git submodule

delete debug log in pika_command.cc

ThreadModle done.
TODO redis response parser, redis command builder.