Add IssueHelper for internal releases to get release task and dedicated issue

What does this MR do and why?

This MR introduces ReleaseTools::InternalRelease::IssueHelper so that the other methods can find and reference the task issue and the dedicated issue.

Dedicated issue hasn't been created yet, but it will be labelled with internal releases , so that's what I put down for now.

Setup step to Internal release pipeline: Create issue on Dedi... (gitlab-com/gl-infra/delivery#20161 - closed), MR to actually implement the dedicated issue: !3986 (merged)

Content

• Add IssueHelper for internal releases to get release task and dedicated issue
• Add gitlab-com/gl-infra/gitlab-dedicated/team as a project