观察 “region_count”: 是否有减小的趋势，直到归 0 变为 tomestone 状态
可修改如下参数进行加速，x根据负载自行根据现在的数值调整：
config set region-schedule-limit x
config set replica-schedule-limit x
config set leader-schedule-limit x
config set max-pending-peer-count x
config set max-snapshot-count x
config set merge-schedule-limit x