Draft: Convert groups form to use dropdown for visibility

What does this MR do?

Changes the visibility selector to be a dropdown instead of radio buttons.

This better aligns with the form used during registration and allows us to consolidate on a standard design for group creation as used during registration

Note: Changelog is in FOSS instead of ee since the ee changes are developer-facing only.

Validate locally

visit http://127.0.0.1:3000/groups/new

Screenshots (strongly suggested)

platform	before	after
desktop
mobile

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #292058