**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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from airflow.models.baseoperator import BaseOperator
from airflow.models.taskmap import TaskMap
from airflow.operators.empty import EmptyOperator
from airflow.operators.python import ShortCircuitOperator
from airflow.serialization.serialized_objects import SerializedDAG
from airflow.stats import Stats
from airflow.utils import timezone
from airflow.utils.state import DagRunState, State, TaskInstanceState
from airflow.utils.trigger_rule import TriggerRule
from airflow.utils.types import DagRunType
from tests.models import DEFAULT_DATE as _DEFAULT_DATE
from tests.test_utils.db import (
    clear_db_dags,
    clear_db_datasets,
    clear_db_pools,
    clear_db_runs,
    clear_db_variables,
)
from tests.test_utils.mock_operators import MockOperator
DEFAULT_DATE = pendulum.instance(_DEFAULT_DATE)
class TestDagRun:
    dagbag = DagBag(include_examples=True)
    def setup_class(self) -> None:
        clear_db_runs()
        clear_db_pools()
        clear_db_dags()
        clear_db_variables()
        clear_db_datasets()
    def teardown_method(self) -> None: