Introduce a new 'security_qa_issue' task

This introduces a new security_qa_issue which is basically SECURITY=true qa_issue[...].

I had to adapt a few places to handle retrieving data from .org.

Here is a sample issue for the 11.1.2 security issue: https://gitlab.com/snippets/1738485

Once this is merged, we'll be able to get rid of .gitlab/issue_templates/Patch-Security-Release-QA-task.md in gitlab-org/release/tasks!43 (merged), and greatly simplify gitlab-org/release/docs!49 (merged) as well.