[Python] Improve type hints of cluster objects (project-chip#29966)

* Use default value for initialization

The default value returns a valid value for the initialization according
to the type hints. This lowers the type hints errors using mypy from 838
to 354.

* Make response_type an optional string if initialized to None

This reduced mypy type errors from 354 to 163.

* Use non-string type annotations

Python 3.7 and newer don't need strings for type annotations anymore.
This makes type annotations more readable in most editors.

* regen

Author: agners