feat(auto-devops): remove mandatory jobs from auto-devops template

With the introduction of mandatory jobs via pipeline execution policies, it is important that the common template doesn't introduce duplicate jobs.

Expand the list of Auto-DevOps templates explicitly. Since GitLab has moved away from a single Auto-DevOps template and towards features requiring explicit opt-in by including templates, it is unlikely that new features will be added to Auto-DevOps in future and so keeping a static list of templates is appropriate.

You can see the before and after effect of these changes on pipelines:

Before:

After:

Without this change, duplicate security scanning jobs are created on pipelines. This, although inelegant, does not introduce errors and so it is a benign wart which means we don't need to encourage people to update their CI templates usage beyond the usual urging.

Closes #139 (closed)