Add Policy Evaluator for Patched Version Availability (Patchable vs Non-Patchable)

### Current Behavior

Dependency-Track policies cannot evaluate vulnerabilities based on whether a patched version exists.

As a result, policies/SLA checks treat all vulnerabilities similarly, even when no upgrade/patch is available.

### Proposed Behavior

Add a new policy evaluator that checks whether vulnerabilities associated with a component have a patched version available.

Policies should be able to trigger when:

1. Patched version is present, or
2. Patched version is not present

based on configured condition (IS / IS_NOT) and expected value (true / false).

### 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