Use templates for security scanners

Some security templates keep changing and they break our pipelines when they are merged to the default branch. We should use a versioned template pointing to a stable branch, e.g.

Decided to use templates again !60 (comment 428136631) to help with Dogfooding the security templates

inclue:
  - template: Dependency-Scanning.gitlab-ci.yml

Related to #56 (closed)

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From reviews in !58 (merged)

We could potentially have a CI job that looks for any changes since 13-3-stable-ee and flags it in the pipeline, in an 'allowed to fail' status?