List users which are oauth enabled

### The required feature described as a wish

As a User/Admin/Operator I would like to list the users which have Ouath enabled

Steps to reproduce the issue

1. Configure Oauth

https://docs.cloudstack.apache.org/en/4.22.0.0/adminguide/accounts.html#using-oauth2-authentication-for-users

2. Create a user account which has the email configured with the oauth provider

3. Login with Oauth

4. Oauth successful

Currently, we can list the users based on usersource

https://cloudstack.apache.org/api/apidocs-4.22/apis/listUsers.html

usersource
List users by their authentication source. Valid values are: native, ldap, saml2 and saml2disabled.

It would nice if we can add Oauth to it

Start with the listUsers API documentation and the OAuth2 authentication guide linked in the issue, then trace how the existing usersource filter handles native, LDAP, and SAML users. Done means listUsers can identify OAuth-enabled users through an OAuth value and the API documentation describes that value.

Written by the indexing model from the issue text.