Add spam icon to issues that are hidden

📖 What does this MR do?

Related to #338751 (closed)

In https://gitlab.com/gitlab-org/gitlab/-/issues/327353 we added the ability to ban a user. In #327355 (closed) we extended the ban functionality so issues created by banned users are hidden. This MR adds a spam icon to the header of the detail view of a hidden issue. Only Admins can see hidden issues, for all other users they will not show in the issue list.

📷 Screenshots

View	Before	After
Desktop
Desktop sticky header
Mobile
Mobile sticky header

💻 How to setup and validate locally

1. Enable the ban_user_feature_flag feature flag
   • bin/rails console
   • Feature.enable(:ban_user_feature_flag)
2. Login as an Admin
3. Navigate to the issue list on a project and make note of the author of an issue
4. Navigate to /admin/users and find the author of the issue
5. From the ⚙ User administration menu select Ban user
6. Navigate back to the issue from step 3

🚦 Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• [-] I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [-] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• [-] I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.