Added Snippet Edit Visibility component

What does this MR do?

The MR refactors the Description field, of Snippet's edit form to Vue.

NOTE: this is a part of a larger effort of refactoring Snippet edit form to Vue and hence is not easily available for click-testing, unfortunately, as not all of the components are ready yet.

How to click-test

1. Turn on the :snippets_edit_vue feature flag: in Rails console (rails c) type Feature.enable(:snippets_edit_vue)
2. Apply the patch: 26799-helper.patch
3. Edit an existing Snippet

Screenshots

Before	After

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

References #207242 (closed)