**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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dag_id=dr.dag_id,
            is_failure_callback=True,
            run_id=dr.run_id,
            processor_subdir=TEST_DAG_FOLDER,
            msg="timed_out",
        )
        assert callback == expected_callback
    def test_dagrun_callbacks_commited_before_sent(self, dag_maker):
        """
        Tests that before any callbacks are sent to the processor, the session is committed. This ensures
        that the dagrun details are up to date when the callbacks are run.
        """
        with dag_maker(dag_id="test_dagrun_callbacks_commited_before_sent"):
            EmptyOperator(task_id="dummy")
        self.scheduler_job = SchedulerJob(subdir=os.devnull)
        self.scheduler_job.processor_agent = mock.Mock()
        self.scheduler_job._send_dag_callbacks_to_processor = mock.Mock()
        self.scheduler_job._schedule_dag_run = mock.Mock()
        dr = dag_maker.create_dagrun()
        session = settings.Session()
        ti = dr.get_task_instance("dummy")
        ti.set_state(State.SUCCESS, session)
        with mock.patch.object(settings, "USE_JOB_SCHEDULE", False), mock.patch(
            "airflow.jobs.scheduler_job.prohibit_commit"
        ) as mock_guard:
            mock_guard.return_value.__enter__.return_value.commit.side_effect = session.commit
            def mock_schedule_dag_run(*args, **kwargs):
                mock_guard.reset_mock()
                return None
            def mock_send_dag_callbacks_to_processor(*args, **kwargs):