Create VulnerabilityType and supporting types

What does this MR do?

• Creates VulnerabilityType
• Creates VulnerabilityReportTypeEnum
• Creates VulnerabilitySeverityEnum
• Creates VulnerabilityStateEnum
• Creates VulnerabilityResolver
• Adds vulnerabilities property to ProjectType

This work will be used on the project security dashboard: #207437 (closed)

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.