Add allowlist rule for secrets analyzer project

Problem to solve

This is a placeholder issue for adding an allowlist rule for the secrets analyzer so that we are not scanning our tests files. Currently the secrets dashboard is full of false-positive secrets from our tests. We should add an allow rule to the gitleaks config which prevents test files from being detected as secrets.

Implementation plan

• Set gitleaks.toml at the project root.
• Add before_script to copy gitleaks.toml to CI build mount for secrets pipeline.
• Ensure downstream test expectations are in the secrets project.
• Resolve false positive vulnerabilities from the secrets project security dashboard.

Links / references

https://gitlab.com/gitlab-org/security-products/analyzers/secrets/-/blob/master/gitleaks/gitleaks.toml