Add visibility level section to organization settings

What does this MR do and why?

Related to #456511

The grouptenant scale team working on building the Organization MVC. For more information about what an "Organization" will be see https://docs.gitlab.com/ee/architecture/blueprints/organization/

For the MVC new organizations can only be private and the "Default" organization will be public. This MR adds visibility level section to organization settings to help lay the groundwork for when it can be changed and also as in indicator as to what visibility level the organization has.

MR acceptance checklist

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Screenshots or screen recordings

Default organization

New organization

How to set up and validate locally

Enable the feature flag

• echo "Feature.enable(:ui_for_organizations)" | gdk rails c

Default organization

1. Go to /-/organizations/default
2. Go to Settings -> General -> Visibility

New organization

1. Go to /-/organizations/new and create an organization
2. Go to Settings -> General -> Visibility