Reduce the number of write buffers for infrequently used column families about kvrocks HOT 9 OPEN

Please assign it to me, thanks a lot :D

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@LiuYuHui Thank you!

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Hi @LiuYuHui Are you still working on this issue?

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Hi @git-hulk, I have had no extra time bandwidth recently, please feel free to assign it to other people.

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@LiuYuHui Thanks for your quick response. Welcome back while you get time.

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Hi @git-hulk , May i question? How do we implement this feature?

1. For each column family add a config, specifying its number of write buffers. eg: pubsub.max_write_buffer_number、propagte.max_write_buffer_number、zset_score.max_write_buffer_number ...
2. Add a lite mode config, When this config is set to true, create a new lite_table_opts for infrequently used column families. like:

rocksdb::BlockBasedTableOptions lite_table_opts = InitTableOptions();
rocksdb::ColumnFamilyOptions lite_opts(subkey_opts);
lite_opts.write_buffer_size = 32 * MiB;
lite_opts.max_write_buffer_number = 0;

// replace subkey_opts with lite_opts 
column_families.emplace_back(kZSetScoreColumnFamilyName, lite_opts);
column_families.emplace_back(kPubSubColumnFamilyName, lite_opts);
column_families.emplace_back(kPropagateColumnFamilyName, lite_opts);
column_families.emplace_back(kStreamColumnFamilyName, lite_opts);```

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