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This will allow implementing our own AddonsProvider in fenix.

This matches the search engines from desktop, that is:
DDG as the default, then YouTube, Google, DDGOnion,
Startpage, Twitter, Wikipedia and Yahoo.

Together with the corresponding fenix patch, this allows all `startActivity`
that may open external apps to be replaced by `TorUtils.startActivityPrompt`.

Prior to https://github.com/mozilla-mobile/android-components/pull/7856 we only had a NotAuthenticated
state, which user would remain in until the very end of the authentication process (receiving a 'finished...' api call).

After the refactor, we introduced an in-progress states - specifically, BeginningAuthentication. If the user
cancels the auth flow (e.g. closes a custom tab), they will remain in this state. Subsequent login attempts
would then fail.

This patch fixes this by introducing a Cancel event which we trigger whenever handling 'beginAuthentication' calls.
In normal scenarios, this event is ignored. Otherwise, it "resets" the state machine into NotAuthenticated
state before emitting any Begin* events.

when resuming a download