Add vulnerability_states for scan_result_policies

What does this MR do and why?

Add vulnerability_states for scan_result_policies as it was done by Vulnerability-Check.

This feature is behind a feature flag (disabled by default) so there is not a concern with migrating existing data.

Related epic: &6604 (closed)

Example of yaml:

scan_result_policy:
- name: critical vulnerability CS approvals
  description: critical severity level only for container scanning
  enabled: true
  rules:
  - type: scan_finding
    branches:
    - master
    scanners:
    - container_scanning
    vulnerabilities_allowed: 1
    severity_levels:
    - critical
    vulnerability_states:
    - detected
    - confirmed
  actions:
  - type: require_approval
    approvals_required: 1
    approvers:
    - adalberto.dare

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