Scan malware advisories with activated "GitHub Advisories" Sources

### Current Behavior

It seems, that Dependency Track doesn't scan for Github malware advisories like:

- https://github.com/advisories/GHSA-3jjr-pvq7-4jq5
- https://github.com/advisories/GHSA-qjqf-7j6f-82c4

Those vulnerabilties can neither be found with the UI on:

/vulnerabilities
/vulnerabilityAudit

Nor directly with /vulnerabilities/GITHUB/GHSA-3jjr-pvq7-4jq5

### Proposed Behavior

Mirror those malware advisories as well as other advisories.

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/master/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this enhancement was already requested