Add poetry.lock file to dependency scanning template

What does this MR do and why?

This MR updates the dependency scanning ci template to run gemnasium-python if a poetry.lock file exists 0-2 levels beneath the working directory. As part of the implementation plan of #7006 (closed), the relevant documentation for this will be updated in !87161 (merged).

Screenshots or screen recordings

How to set up and validate locally

1. Import the test python-poetry project locally.
2. Create a new branch and update the .gitlab-ci.yml:

   stages:
     - test
     - qa
   
   include:
     # Security Products features
     - template: Jobs/Dependency-Scanning.gitlab-ci.yml
   
     # Security Products features QA
     - https://gitlab.com/gitlab-org/security-products/ci-templates/raw/master/includes-dev/qa-dependency_scanning.yml

3. Trigger a pipeline run with the variable DS_MAJOR_VERSION set to 3.
4. The pipeline should security widget should show the poetry.lock deps found.

MR acceptance checklist

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