Hitting 'resend all' can result in duplicates

If you send 'resend all' during bad connectivity, then it may disappear but not appear to have resent anything. It then reappears, and you hit it again, and repeat again... and discover you resent in triplicate.

Start by reproducing the issue in the Element iOS app: use “resend all” during bad connectivity and observe the pending messages. Trace the resend action and its handling of connectivity or retry state; done means repeated taps do not send the same messages more than once.

Written by the indexing model from the issue text.