UX improvements
- !oncall_now auto figures out what escalation is requested
- !sre_paged_now, which was doing that for SREs, is removed
- !incidents prints a message if no incidents happened in the last 24 hours
- !refresh_topic by default tries to act on the topic of the channel where it's called
- Do not ping nicks when someone asks who's oncall in a public channel (thanks rzl!)
- Verify we managed to change the topic of a channel
Bug: T314843