The helm-chart should not force the settings of Resultsbackend, Metadata and Broker. Either through an additional configuration option or implicitly by not providing values, the helm-chart should refrain from populating those Airflow-Env configurations.

**Use case / motivation**
The current Helm chart forces the configuration of certain values such as `brokerUrl` (https://github.com/apache/airflow/blob/main/chart/values.yaml#L236)
Which will then be populated as Airflow ENV config.
Due to Airflows configuration precedence (https://airflow.apache.org/docs/apache-airflow/stable/howto/set-config.html) are these settings taking highest priority in Airflow configuration.

With the suggested change, users can dynamically provide Airflow configurations through Airflow's `__CMD` environment variables.

**In other words; provide users with the option to utilize Airflow's `__CMD` ENV configuration.**

_I am willing to submit a PR._

chart/tests/test_airflow_common.py
#
#
import jmespath
import pytest
from parameterized import parameterized
from tests.helm_template_generator import render_chart
class TestAirflowCommon:
    """
    This class holds tests that apply to more than 1 Airflow component so
    we don't have to repeat tests everywhere
    The one general exception will be the KubernetesExecutor PodTemplateFile,
    as it requires extra test setup.
    """
    @parameterized.expand(
        [
            ({"gitSync": {"enabled": True}}, True),
            ({"persistence": {"enabled": True}}, False),
            (
                {
                    "gitSync": {"enabled": True},
                    "persistence": {"enabled": True},
                },
                True,
            ),
        ]
    )
    def test_dags_mount(self, dag_values, expected_read_only):