Organization overview for instance admins

Problem

Once Organizations exist, we will need to give instance admins the ability to manage all the Organizations of their instance. We need to:

1. Decide which functionality should be available in the Organization overview (create new Organization?, delete Organization?, edit name and path?)
2. Where the Organization overview will appear

Proposal

This Organization overview could live in the current Admin Area and provide a path into Organizations, particularly for self-managed customers to help with the transition of a lot of the current Admin Area functionality into the Organization. Designs could be heavily oriented on the existing Groups overview.

Designs - Figma

Implementation guide

1. Add organizations route to config/routes/admin.rb#L13
2. Create app/controllers/admin/organizations_controller.rb with an index action
3. Create app/views/admin/organizations/index.html.haml
4. Create app/assets/javascripts/admin/organizations/index.js
5. Move app/assets/javascripts/organizations/index/components/organizations_list_item.vue, app/assets/javascripts/organizations/index/components/organizations_list.vue, and app/assets/javascripts/organizations/index/components/organizations_view.vue into app/assets/javascripts/organizations/shared/components
6. Create app/assets/javascripts/admin/organizations/components/app.vue that renders app/assets/javascripts/organizations/shared/components/organizations_view.vue
7. Use GraphQL query added in GraphQL query for listing all organizations in ... (#431756 - closed) for data