**Description**

It would be nice if the weight_rule default value could be managed by a global config

suggested config:
```
# Weighting method used for the effective total priority weight of the task. 
# Options are: { downstream | upstream | absolute } default is
default_weight_rule = downstream
```
**Use case / motivation**

In some pipeline, you really need to have absolute weight, and then you have to add a line in each task definition which is annoying

tests/core/test_configuration.py
"""Test AirflowConfigParser.getfloat"""
        test_config = """
[invalid]
key1 = str
[valid]
key2 = 1.23
"""
        test_conf = AirflowConfigParser(default_config=test_config)
        with pytest.raises(
            AirflowConfigException,
            match=re.escape(
                'Failed to convert value to float. Please check "key1" key in "invalid" section. '
                'Current value: "str".'
            ),
        ):
            test_conf.getfloat('invalid', 'key1')
        assert isinstance(test_conf.getfloat('valid', 'key2'), float)
        assert 1.23 == test_conf.getfloat('valid', 'key2')
    def test_has_option(self):