Get project root ref and verify file path

What does this MR do and why?

Get project root ref and verify file path

• use root ref for verification of file path of code action block

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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Before	After
N/A	root_ref_validation

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Enable the feature flag echo "Feature.enable(:compliance_pipeline_in_policies)" | rails c.
3. Navigate to a group => Settings => General => Permissions and group features => Enable Security policy pipeline execution action
4. Navigate to a project in the group => Secure => Policies => New policy => Scan Execution Policy
5. Click Add action => Run CI/CD code => Run Linked existing CI file
6. Verify nothing is outlined in red
7. Select the current project you are in as the project
8. Type in .gitlab/security-policies/policy.yml as the file
9. Verify that the verification fails
10. Change the project to the security policy project you selected in Step 3
11. Verify that the verification succeeds

Related to #443341 (closed)