[WarnSystem] Replace role mute system, with Discord built-in timeouts

[Luc1412]

Pull request type

This PR replaces the old role-based mute system, with Discord's timeouts.

Description of the changes

• Duration for warns with level 2 are now mandatory and are limited to 28d
• Removed everything related to role management and role settings for mutes
• Mutes got renamed to timeouts
• Warn System doesn't require role management related permissions, instead it requires moderate members permission

Check-list

If useful, make a bullet list of the things done or not (will show up in the PR list). Example:

• Properly naming command to remove timeouts
• Require time for warn level 2 and check if it's within 28d in API
• Should we handle unmutes? If so, how?
• Testing