Load vulnerabilities for instance dashboard

What does this MR do?

Loads the vulnerabilities from GraphQL in the Instance Level Dashboard. This is the first MR of a bigger feature - so it seems incomplete. Other MRs will follow soon.

Screenshots

Local Development

Testing this feature requires the following:

• An EE license. See https://about.gitlab.com/handbook/developer-onboarding/#working-on-gitlab-ee.
• The following feature flags enabled. first_class_vulnerabilites

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team