This PR makes it so the channel list will still be shown while
reconnecting to Collab instead of showing the signed-out state.

In order to model the transitional states that occur while reconnecting,
we needed to introduce a new `Status::Reauthenticated` state that we go
through when signing in as part of a reconnect. This is because we
cannot tell from `Status::Authenticated` alone if we're authenticating
for the first time or reauthenticating.

Release Notes:

- N/A