* Utils.py: add _find_cache_attributes, clear_method_caches

* TestCythonUtils.py: add tests for Cached Methods

* Utils.py: add constants

* Utils.py: update comment

* TestCythonUtils.py: remove excess blank line

* Change names to `_CACHE_NAME` and `_CACHE_NAME_PATTERN`

* ci.yml: extend timeout to 40 minutes

* _CACHE_NAME -> _build_cache_name