Jira Issue Detail page: Jira private links with paperclip icons

What does this MR do?

Follow-up from !54098 (merged).

In the Jira Issue Detail page, this adds the paperclip icon before the Jira private image links.

The changes adding the paperclip icon are under the jira_issues_show_integration feature flag but the changes on the sanitization filter have a direct impact in the system.

Before	After

Related to #320976 (closed)