Use DB where possible for quicker ``airflow dag`` subcommands (#21793)
Use DB where possible for quicker ``airflow dag`` subcommands (#21793)

Some of the subcommands here don't actually need a full dag, so there is
no point paying the (possibly long) time to parse a dagfile if we could
go directly to the DB instead.

Closes #21450


Acehaidrey/incubator-airflow,nathanielvarona/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,apache/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,nathanielvarona/airflow,lyft/incubator-airflow,cfei18/incubator-airflow,lyft/incubator-airflow,lyft/incubator-airflow,apache/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,danielvdende/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,nathanielvarona/airflow,apache/airflow,danielvdende/incubator-airflow,apache/airflow,cfei18/incubator-airflow,cfei18/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow