GraphQL API: Support queries used in Projects::Settings::CiCdController#define_runners_variables

Description

This issue depends on #328518 (closed), and will be used to build #33803.

In #328518 (closed) we defined a list of runners for administrators, and now we should do the same for projects.

query getProjectRunners() {
  # Return all runners that are available for use by this project, as shown in the CI CD settings
  project(fullPath: "my-project") {
    runners( 
        membership: "DIRECT", # CiRunnerProjectMembershipFilter
        before: "...", # Pagination arguments
        after: "...",
        first: "...",
        last: "..." ) {
      nodes { # CiRunner
        id
      }
    }
  }
}

Feature parity requirements:

This GraphQL API to create the UI described at: #33803[Project-runners.png], which will replace our legacy runner UI.

Runners in the list can be filtered by: Project, Group or Instance, which should correspond to the 4 lists fetched by our current UI:

• Project: @project_runners + @assignable_runners (the list is separate in the original UI, we can consider merging it in the new UI, or adding @assignable_runners as a new list)
• Instance: @shared_runners
• Group: @group_runners

Implementation plan

The following table summarizes the queries we'll need to provide in order to replace the existing UI and queries that are currently embedded in the controller:

variable	query	location
@shared_runners	project { runners(type: INSTANCE_TYPE, paused: false) }	https://gitlab.com/gitlab-org/gitlab/blob/9d2d05be54a378581883c00337894288d1ef2efd/app/controllers/projects/settings/ci_cd_controller.rb#L129-129
@group_runners	project { runners(membership: PARENT_GROUPS) }	https://gitlab.com/gitlab-org/gitlab/blob/9d2d05be54a378581883c00337894288d1ef2efd/app/controllers/projects/settings/ci_cd_controller.rb#L133-133
@project_runners	project { runners(membership: DIRECT) }	https://gitlab.com/gitlab-org/gitlab/blob/9d2d05be54a378581883c00337894288d1ef2efd/app/controllers/projects/settings/ci_cd_controller.rb#L120-120
@assignable_runners	project { assignableRunners }	https://gitlab.com/gitlab-org/gitlab/blob/9d2d05be54a378581883c00337894288d1ef2efd/app/controllers/projects/settings/ci_cd_controller.rb#L122-124

• Implement blocker #383510
• Implement assignableRunners field in Types::ProjectType