[AIRFLOW-5245] Add more metrics around the scheduler (#5853)
[AIRFLOW-5245] Add more metrics around the scheduler (#5853)


(cherry picked from commit 698c38b18982bdbcdff55e4648e636b5a722394f)

owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow