aspects.py: Fix/improve the type hints
aspects.py: Fix/improve the type hints

- Page is not imported directly into the module and type checkers won't
  recognize it. Use pywikibot.Page instead.
- To annotate arguments it is preferred to use abstract collection types,
  but for return type, more specific types are preferred. Therefore,
  use pywikibot.BasePage for argument types and pywikibot.Page for
  return types.

Change-Id: I6fcb0478bd9050eb30a7395540cb050e864e165b

wikimedia/pywikibot-core,wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core