On Android, users were unable to join or create multiplayer rooms. The
root cause of that was that the both the wait and set of the
`ManualResetEvent` in `getRoomUsers` occurred on the same thread, which
created a chicken-and-egg situation - the set could not proceed until
the wait had actually completed.
Resolve by substituting the `ManualResetEvent` for a
`TaskCompletionSource` to achieve a promise-style task, which the
previous code was a crude approximation of anyway.
Closes#11385.
These can occur when a network connection is completely unavailable (ie.
host resolution failures are occurring). Currently these would appear as
important errors which spammed the notification overlay every retry
forever, while no network connection is available.
I also took this opportunity to remove a lot of `bool` passing which was
no longer in use (previously the fail count / retry process was
different to what we have today).
It needs to be explicitly stated that the users in this list are related
to the *joined* room. Especially since it's sharing its variable name
with `SpectatorStreamingClient` where it has the opposite meaning (is a
list of *globally* playing players).