[BE] Add ability to filter by provisioned users

This is the backend counterpart to #349887 (closed)

Today within a project/group, you can have a mixture of provisioned and non-provisioned users, but there is no way to filter by this status.

We added an "Enterprise User" badge in #325712 (closed), It would be great if we could filter by badges (also SAML)

Required work

Currently we show the Enterprise badge iff the provisioned_by_this_group? method is true. To support filtering by enterprise users we should add filtering support for this method in the following places:

• Add filter_members method to ee/app/finders/ee/group_members_finder.rb that extends CE filter_members method.
  • Query string parameter can be provisioned_by_this_group=true
• For parity, update REST API to support filtering by Enterprise users.
• For parity, update GraphQL API to support filtering by Enterprise users

Availability and Testing

• Adding unit/integration tests should suffice for this change. No E2E test needed at this time.