Add vulnerability history to graphql

What does this MR do?

This MR adds fields to GraphQL for fetching vulnerability history data. It fetches data in chunks of 10 days to avoid overloading the database. In a future MR, the results will be cached daily to further improve performance.

• Adds vulnerability_severities_count_by_day fields to QueryType and GroupType
• Adds VulnerabilitySeverityCountType, which represents the number of vulnerabilities for a specific day and severity
• Adds VulnerabilityHistoryResolver, which concatenates queries for vulnerability history
• Extracts VulnerabilitiesBaseResolver to encapsulate complex logic for selecting vulnerable object

Issue: Back 'Vulnerabilities over time' report with Standalone Vulnerability data on Instance & Group Security Dashboard

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.