calcute max hashrate based on metric.

CheckStsAutoScalingInterval would check whether there is enough interval duration between every two auto-scaling.

caculated resource cannot exceed cluster limit.

transfer hashrate to tidb replicas.

AnnLastSyncingTimestamp records last sync timestamp.

AnnTiDBLastAutoScalingTimestamp is annotation key of tidbcluster to indicate the last timestamp for tidb auto-scaling.

AnnTiKVLastAutoScalingTimestamp is annotation key of tidbclusterto which ordinal is created by tikv auto-scaling.