This reworks error handling of "use security key" so we stop the overall
operation when cancelling access (instead of just the immediate prompt). In
addition, flowing the error to outer catch block also handles resetting state to
re-display the initial verification choices.
Fixes https://github.com/vector-im/element-web/issues/15584
This adds various customisations point in the app for security related
decisions. By default, these do nothing, but would be customised at the
app level via module replacement (so that no changes are needed here in the
SDK).
Fixes https://github.com/vector-im/element-web/issues/15350