chore: Add flaky test marker for failing downloads

[cbueth]

Description

This PR adds decorators to mark tests as xfail if they are failing due to failing downloads. When testing we request the GHSL download which might fail if sending many tests. Dues to this scheduled tests were failing.

The test marker @mark_xfail_flaky_download already exists, so this PR only adds it to further tests which need it.

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to change)
• 📝 Documentation update
• 🧹 Code refactor (no functional changes)
• ✅ Test update

How Has This Been Tested?

To be tested in CI

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation
• My changes generate no new warnings
• I have added tests that prove my fix/feature works
• New and existing tests pass locally