**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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"""Decrement stat."""
    @classmethod
    def gauge(cls, stat, value, rate=1, delta=False, tags=None):
        """Gauge stat."""
    @classmethod
    def timing(cls, stat, dt, tags=None):
        """Stats timing."""
    @classmethod
    def timer(cls, *args, **kwargs):
        """Timer metric that can be cancelled."""
        return Timer()
ALLOWED_CHARACTERS = set(string.ascii_letters + string.digits + "_.-")
def stat_name_default_handler(stat_name, max_length=250) -> str:
    """
    Validate the StatsD stat name.
    Apply changes when necessary and return the transformed stat name.
    """
    if not isinstance(stat_name, str):
        raise InvalidStatsNameException("The stat_name has to be a string")
    if len(stat_name) > max_length:
        raise InvalidStatsNameException(
            f"The stat_name ({stat_name}) has to be less than {max_length} characters."
        )
    if not all((c in ALLOWED_CHARACTERS) for c in stat_name):
        raise InvalidStatsNameException(
            f"The stat name ({stat_name}) has to be composed of ASCII "
            f"alphabets, numbers, or the underscore, dot, or dash characters."
        )
    return stat_name
def get_current_handler_stat_name_func() -> Callable[[str], str]: