Monitoring go runtime by runtime/metrics package

[zyguan]

Enhancement

runtime/metrics has been introduced to stdlib since go1.16, and we are also allowed to monitor sched latency after go1.17. However, the prometheus client that tidb used is v1.11.0 currently, which still gathers runtime metrics from runtime.MemStats. To integrate runtime/metrics, we can simply bump prometheus client to v1.12.2 and use the new go collector.