**Description**


It would be great if the metrics we publish in Airflow change to include TAGs for "variable" parts of those (such as dag_id, task_id, pool name) rather than being part of the metrics.

See here: https://airflow.apache.org/docs/1.10.12/metrics.html, https://airflow.readthedocs.io/en/latest/logging-monitoring/metrics.html  - those variable parts should be tags.

We might consider to change those metrics by default in 2.0 and possibly introduce a backport in 1.10.13 to allow people to migrate.


**Use case / motivation**

Having the variable parts of the metrics makes it really difficult to aggregate the metrics. Seems that statsd python library does not support tags, but there are possible solutions by installing extensions:

https://stackoverflow.com/questions/49852654/sending-statsd-metrics-with-tags-from-python-client

**Related Issues**

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"""
        Test that ignore_first_depends_on_past doesn't affect results
        (this is the same test as
        test_dagrun_deadlock_ignore_depends_on_past_advance_ex_date except
        that start_date == execution_date so depends_on_past is irrelevant).
        """
        self.evaluate_dagrun(
            dag_id="test_dagrun_states_deadlock",
            expected_task_states={
                "test_depends_on_past": State.SUCCESS,
                "test_depends_on_past_2": State.SUCCESS,
            },
            dagrun_state=State.SUCCESS,
            run_kwargs=dict(ignore_first_depends_on_past=True),
        )
    @pytest.mark.parametrize(
        "configs",
        [
            {("scheduler", "standalone_dag_processor"): "False"},
            {("scheduler", "standalone_dag_processor"): "True"},
        ],
    )
    def test_scheduler_start_date(self, configs):