Create a release/task issue for internal releases

Context

Remediating GiLab SaaS single-tenant instances, like GitLab Dedicated, within remediation SLAs requires introducing a new GitLab release strategy: Internal Releases. This release will generate private packages to be delivered to GitLab SaaS single-tenant instances without initiating a patch.

As with any other GitLab release process, a release/task issue will be opened and automatically assigned to release managers with the steps required to perform an internal release

Create a release/task issue for internal releases

1. Similar to patch and monthly issues, implement a new issue class for internal releases
2. The issue should be created in the release/task repository, assigned to release managers and confidential.
3. The template will be introduced by #20615 (closed), in the meantime it can use an empty template
4. The issue should have a method to invoke the internal release pipeline. Configured on #20613 (closed)