Fix or remove Android notifications

This issue is to keep track of old open tickets related to TBA notifications.

#28800 "Implement New Identity functionality for Tor Browser on Android" (We'll probably want an in app button as well, like desktop)

#41231 "Re-design New Identity on Android" (Have it clear everything instead of just getting a new circuit, but we don't actually have it implemented at all currently)

#30618 (closed) "TorBrowser Android reporting wrong bandwidth label units bit/s instead byte/s" (Unsure if it's still an issue or if we even still want to display that data)

#31037 Add 'Quit' action button in Tor Browser for Android persistent notification. (We kind of have this implemented currently, but you need to have at least one tab open for it to show up)

#43179 TBA alpha and Firefox notifications are identical

Other observations:

1. It seems that sometime between 13.0 release (shown as Tor Browser below) and 13.5a7 (shown as Tor Browser Alpha below) the "New Identity" button was removed entirely in favor of "Close private tabs" so we'll want to re-add that(?). @dan Thoughts on this?

2. The icon went from an onion to a mask.

Below I also have a private FireFox tab open and Orbot open to show some other UI examples. @donuts any ideas for how we want this to look?