Type check all helpers (#25373)

* Type check all helpers, add inline exclusions for work in progress

* Remove unused Script._template_cache

* Add some missing type hints

* Remove unneeded type: ignore

* Type hint fixes

* Mypy assistance tweaks

* Don't look for None in deprecated config "at most once" check

* Avoid None name slugify attempt when generating entity id

* Avoid None state store attempt on entity remove

homeassistant/helpers/device_registry.py

@@ -12,6 +12,10 @@ from homeassistant.loader import bind_hass
 
 from .typing import HomeAssistantType
 
+
+# mypy: allow-incomplete-defs, allow-untyped-calls, allow-untyped-defs
+# mypy: no-check-untyped-defs, no-warn-return-any
+
 _LOGGER = logging.getLogger(__name__)
 _UNDEF = object()