Update addons notification features

[ben-c-at-moz]

Given the logic in the notifications base and addons files, update https://github.com/mozilla/FoxPuppet/blob/main/foxpuppet/windows/browser/notifications/addons.py so that unfinished methods are completed.

• Make sure there is a class for each type of notification
• Each notification class should have class methods appropriate to it

Add tests as needed, and make sure they pass (and that all others do too), using make test and in CI.

[Temidayo32]

I am looking into this issue