(Partial)Guild(Id)::audit_logs takes in raw action type IDs instead of the Action enum

[pluiedev]

Currently, serenity::model::Guild::audit_logs (as well as the equivalent methods in GuildId and PartialGuildId) take an Option<u8> for the optional action type field. This is incredibly bad for multiple reasons, such as allowing the user to easily and mistakenly specify incorrect type IDs, and requiring a comment explaining the magic number in many cases.

Since Serenity already has an Action enum that models this action type very clearly, we should definitely refactor the audit_log methods to use this enum in 0.12.x.