Add metric prometheus_rule_group_last_evaluation for recording and alerting (#4852)
Add metric prometheus_rule_group_last_evaluation for recording and alerting (#4852)

* add metric prometheus_rule_group_last_evaluation for recording and alerting

Signed-off-by: Wei Guo <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@imkira.com>

* fix issues from comments

Signed-off-by: Wei Guo <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@imkira.com>

Gouthamve/prometheus,keegancsmith/prometheus,kangwoo/prometheus,GoogleCloudPlatform/prometheus,keegancsmith/prometheus,alileza/prometheus,keegancsmith/prometheus,Gouthamve/prometheus,prometheus/prometheus,prometheus/prometheus,prometheus/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,alileza/prometheus,keegancsmith/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,Gouthamve/prometheus,GoogleCloudPlatform/prometheus,kangwoo/prometheus,kangwoo/prometheus,prometheus/prometheus,alileza/prometheus,GoogleCloudPlatform/prometheus,alileza/prometheus,Gouthamve/prometheus,prometheus/prometheus,keegancsmith/prometheus