[RoleUtils] auto role support

[phenom4n4n]

Add support for auto roles and sticky roles.

• auto role list should be cached on init and modified with commands make sure to modify cog mixin inits to accept one Config.all_members call on initialization and pass it to each mixin before adding it to the bot
• auto roles and sticky roles should wait until the member passes verification if the guild has welcome rules enabled. this is a bit tricky since i'll have to decide whether or not there should be a timeout while waiting for verification, and also decide whether a leave listener should be added to return early
• check whether roles can be added before adding them