During migration of Poll plugin from widget basis to glimmer, some functionality was inadvertently dropped:
- A single button should appear instead of the dropdown menu when there is only one valid "poll admin" action
- No button should appear when there are no valid "poll admin" actions for current user
This PR restores the original behaviour and adds test coverage (that didn't exist prior to migration, partly why it wasn't caught earlier)
relates to #27204
related meta topic: https://meta.discourse.org/t/what-is-the-gear-button-under-the-poll-for/315477/2
d8d3d2184a