Enhancement

ref pingcap/tiflash#6620
ref pingcap/tiflash#7084

New MPP Version (release-6.6)

support mpp-version in planner

• planner: add MppVersion for mpp task; support data compression in Exchange Operator; #40132
• mpp: add mpp versoin and data packet version kvproto#1027

MPP Exchange Data Compression (release-6.6)

support data compression in exchange operator

• executor: exchange operator supports data compression tipb#285

New Cost Model Of Broadcast Join (release-7.1)

• planner: support data compression in Broadcast / Passthrough exchange operator; optimize process about choosing Broadcast Join; #41968
• planner: disable tidb_prefer_broadcast_join_by_exchange_data_size by default; set scale factor to optimize estimating broadcast join; #42915