Reduce time for /events

[en3sis]

After adding the new plugin for /events, I notice that in servers with many events & users, the command is slow.

Possibles causes:

• https://github.com/en3sis/hans/blob/main/src/controllers/plugins/events.controller.ts#L11
• https://github.com/en3sis/hans/blob/main/src/controllers/plugins/events.controller.ts#L15

Since the participants are not part of the GuildScheduledEvent and we need to fetch them for each event, that seems to be a heavy computation, we might be able to improve this by further checks and exceptions.

[en3sis]

Some initial work was commited here and 206c70d