Refactor toast to alert in Image Repository details

What does this MR do?

This MR swap away from the toast message that informs the user about the successful (or not ) deletion of tags. The alert has an additional message if the user performing the deletion is an admin recommending him to run the garbage collection

In addition, this MR fixes an edge case with a ghost delete (if the user check the box of a row and then performs a single delete)

Screenshots

Succesful delete

As non-admin

As an Admin

Not successful delete (same for user and admin)

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 #214477 (closed)