RBO rules supplement

[KKould]

Feature Request

• max-min-eliminate
  • ref: https://docs.pingcap.com/zh/tidb/stable/max-min-eliminate
• correlated-subquery-optimization
  • ref: https://docs.pingcap.com/zh/tidb/stable/subquery-optimization
• predicate-pushdown
  • outer -> inner, ref: link
• outer_join_eliminate
  • ref: https://cn.pingcap.com/blog/tidb-source-code-reading-21/
• aggregation_push_down
  • ref: https://www.openpie.com/community/blog/1284050105

[KKould]

Skyline-Pruning