Show object access warning when disabling repo LFS

What does this MR do?

For #19965 (closed).

When disabling the Git Large File Storage option in the repo settings, if the project has any LFS objects, a small informational message is displayed. The message indicates that objects are still available to forks, and provides a link to learn how to remove those objects. This message remains below the toggle until there are either no more objects in the repository or LFS is turned back on.

Screenshots

Before this change, the LFS toggle doesn't warn that LFS files could be accessible from forks:

After this change, some information is included, as well as a link to documentation to remove the LFS files:

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