Improvements

• The v2 algorithm of the hot Region scheduler becomes GA. In some scenarios, the v2 algorithm can achieve better balancing in both configured dimensions and reduce invalid scheduling #5021 @HundunDM
• Optimize the timeout mechanism of operator step to avoid premature timeout #5596 @bufferflies
• Improve the performance of the scheduler in large clusters #5473 @bufferflies
• Support using external timestamp which is not provided by PD #5637 @lhy1024

Bug fixes

• Fix inaccurate Stream timeout and accelerate leader switchover #5207 @CabinfeverB