Move Security vendored templates into the Jobs subdir - part 1

Summary

With the recent changes of Composable AutoDevops, a new directory call Jobs has been created for the purpose of per job templates that needs to be used with the include feature.

This is exactly what our Security vendored templates are for so we should make this consistent.

Proposal

• Move templates to the [Jobs](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Jobs subdir
• Change the existing CI templates (in Security) so that they include the new ones (in Jobs), with a code comment explaining that change. See https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/gitlab/ci/templates/Security/SAST.gitlab-ci.yml

Notes on the proposal:

• We keep Security reference in ADO template and doesn't change it.
• We don't change references in the documentation.

NB: as a side effect of this change, the vendored template won't be discoverable anymore as they won't be listed in the template dropdown in Gitlab UI. Providing a way to discover and include job templates via the UI is being addressed in #job in #24939 (closed)

Testing

Implicitly test with integration tests and test projects