Add filtering active and human users in GraphQL

What does this MR do and why?

This MR adds filtering of the users GraphQL field to return only human users and only active users, through new optional active: BOOLEAN and human: BOOLEAN arguments.

When the arguments are not provided the field will return the same users as it does currently.

UsersFinder has been updated to allow scoping only human users.

This work is to allows returning only active human users within a user mapping search.

#471933

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

In a Rails console find an active user, deactivated user, and bot user

active_user = User.active.take
deactivated_user = User.deactivated.take
bot_user = User.bots.take

Find their Global IDs, which will be passed in as the ids: argument to the GraphQL Query.users field:

active_user.to_global_id.to_s
deactivated_user.to_global_id.to_s
bot_user.to_global_id.to_s

Make queries passing in those user IDs. Note that UsersFinder's definition of active excludes non-internal users due to the User scope so you can't find active bot users. This is also the behaviour of the REST API. It seems best to use existing finder-supplied scoping.

Only humans:

{
  users(humans: true, ids: [<GLOBAL_ID>]) {
    nodes {
      username
    }
  }
}

Only active (non-internal) users:

{
  users(active: true, ids: [<GLOBAL_ID>]) {
    nodes {
      username
    }
  }
}

Related to #471933