**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

airflow/configuration.py
if is_sqlite:
            import sqlite3
            from distutils.version import StrictVersion
            from airflow.utils.docs import get_docs_url
            
            min_sqlite_version = '3.15.0'
            if StrictVersion(sqlite3.sqlite_version) < StrictVersion(min_sqlite_version):
                raise AirflowConfigException(
                    f"error: sqlite C library version too old (< {min_sqlite_version}). "
                    f"See {get_docs_url('howto/set-up-database.html#setting-up-a-sqlite-database')}"
                )
        if self.has_option('core', 'mp_start_method'):
            mp_start_method = self.get('core', 'mp_start_method')
            start_method_options = multiprocessing.get_all_start_methods()
            if mp_start_method not in start_method_options:
                raise AirflowConfigException(
                    "mp_start_method should not be "
                    + mp_start_method
                    + ". Possible values are "
                    + ", ".join(start_method_options)
                )
        if self.has_option("scheduler", "file_parsing_sort_mode"):
            list_mode = self.get("scheduler", "file_parsing_sort_mode")
            file_parser_modes = {"modified_time", "random_seeded_by_host", "alphabetical"}
            if list_mode not in file_parser_modes:
                raise AirflowConfigException(
                    "`[scheduler] file_parsing_sort_mode` should not be "
                    + f"{list_mode}. Possible values are {', '.join(file_parser_modes)}."
                )
    def _using_old_value(self, old, current_value):