Use "server" time from default.cfg for template engine variables

[MaksYermak]

In Airflow configuration we have the ability to change the default_timezone and then use this time like Server time. But for our template engine variables we continue to change time to UTC timezone e.g. execution_date https://github.com/apache/airflow/blob/main/airflow/models/taskinstance.py#L546

Community, what do you think about adding a new functionality which checks default_timezone and if default_timezone is not UTC then converts time to a new specified timezone?