Fixing various issues in utils folder reported by MyPy

[khalidmammadov]

Part of #19891

Fixes number of issues reported by MyPy:

• Provide explicit type for dates variable
• states_by_task_id is not Optional as functions upstream and downstream are not that passes the same variable
• render_dag_dependencies function's only parameter is not optional as it does not handle that case nor anywhere in the codebase it is accessed as empty
• self.filename_template and self.filename_jinja_template are Optional and hence need to be handled accordingly inside _render_filename function
• Handling case when regex does not match anything
• Providing possible types for "template_env" variable explicitly
• Removed Overloading for the functions. I don't see any reason why they are necessary. @ashb Please comment otherwise as they were added in Improve handling edge-cases in airlfow.models by applying mypy #20000
• Better handling for dynamic field access for localize and convert methods
• relativedelta does not define type for seconds and accepts float (I tested empirically) as well which MyPy complains that is not allowed. So, ignoring
• MyPy dont understand that v in pendulum.instance(v can not be None as previous check and hence failing
• Added one more test case for correct_maybe_zipped to check for an empty input

This is Part 1 for (airflow/utils) and will do Part 2 in a separate PR to keep scope small for review and focus.

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[khalidmammadov]

Closing in favor of #20482