Setup boilerplate for organization group edit

What does this MR do and why?

Related to #410810

The grouptenant scale team is starting to build out an Organization MVC. For more information about what an "Organization" will be see https://docs.gitlab.com/ee/architecture/blueprints/organization/

This MR sets up the route, controller, and basic Vue app to be able to edit a group an the organization level.

Future MRs

• Update Edit action on list view to link to this page
• Render Vue form (/app/assets/javascripts/groups/components/new_group_form.vue) to edit group

MR acceptance checklist

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Screenshots or screen recordings

How to set up and validate locally

1. Enable the feature flag
   • echo "Feature.enable(:ui_for_organizations)" | gdk rails c
2. Navigate to /-/organizations/default/groups_and_projects
3. Find a group and copy the path to that group (e.g. foo-bar/baz)
4. Navigate to /-/organizations/default/groups/foo-bar/baz/edit