Write an SQL query to identify any overlapping `vc_events`

[dudeofawesome]

• Should identify events whose connection_start and connection_end intervals overlap
• Should look at vc_events per user & guild. (vc_events contains events from multiple users, not just a single user, but multiple users could reasonably have overlapping events.
  • This could either look at all users in a single query, or just a single user in a single query.
• Should ideally return a list of overlapping events, but a count of overlapping events would also be good.
• Should be optionally timeboxed to prevent looking at very old events (maybe default to looking at events newer than guild.last_reset).