This CL mainly changes: 1. Add star schema benchmark tools in `tools/ssb-tools`, for user to easy load and test with SSB data set. 2. Disable the segment cache for some read scenario such as compaction and alter operation.(Fix #6924 ) 3. Fix a bug that `max_segment_num_per_rowset` won't work(Fix #6926) 4. Enable `enable_batch_delete_by_default` by default.