Kick all inactive users

## Describe the feature
The goal is to remove all inactive users from the server via a simple command and later on via a scheduled task.

Here's the list of requirement one user must have to be considered inactive:
- [ ] Has no roles (except the ones automatically given when joining the server)
- [ ] Has been on the server for at least three months.
- [ ] Has sent less than 10 messages in the last month

When using the command, @Grace should show the number of people who will be kicked and then propose (via buttons) if we want to proceed or not.
- [ ] When pressing on `Ok`, all the listed users must be kicked from the server with a message that explains the reason.
- [ ] When pressing `Cancel`, the operation is cancelled and shows the issuer that the it did it successfully

**IMPORTANT**
This command **must** be available to **admin only**.

### Additional information
The function should be place somewhere where it can easily reused (perhaps in the `services` package) since it's going to be used by different part of @Grace (command and scheduler).

The command can simply be added to the `moderation_cog`.