**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**

<!-- Is there currently another issue associated with this? -->

from sqlalchemy.orm import Session
from tabulate import tabulate
import airflow.models
from airflow.api_internal.internal_api_call import internal_api_call
from airflow.callbacks.callback_requests import CallbackRequest, SlaCallbackRequest
from airflow.configuration import conf
from airflow.dag_processing.processor import DagFileProcessorProcess
from airflow.models import errors
from airflow.models.dag import DagModel
from airflow.models.dagwarning import DagWarning
from airflow.models.db_callback_request import DbCallbackRequest
from airflow.models.serialized_dag import SerializedDagModel
from airflow.stats import Stats
from airflow.utils import timezone
from airflow.utils.file import list_py_file_paths, might_contain_dag
from airflow.utils.log.logging_mixin import LoggingMixin
from airflow.utils.mixins import MultiprocessingStartMethodMixin
from airflow.utils.net import get_hostname
from airflow.utils.process_utils import (
    kill_child_processes_by_pids,
    reap_process_group,
    set_new_process_group,
)
from airflow.utils.session import NEW_SESSION, provide_session
from airflow.utils.sqlalchemy import prohibit_commit, skip_locked, with_row_locks
class DagParsingStat(NamedTuple):
    """Information on processing progress."""
    done: bool
    all_files_processed: bool
class DagFileStat(NamedTuple):