Add `Project.isLatest` to notification subjects

### Current Behavior

At the moment, the subject.project category in the notification proto does not have the ability to filter by `isLatest`.

https://github.com/DependencyTrack/dependency-track/blob/e22f0b980860f7a6814af1b945607b3bdbc74e7b/notification/api/src/main/proto/org/dependencytrack/notification/v1/notification.proto#L174-L182

### Proposed Behavior

By adding `isLatest` to the notification propo, it will be easier to get the latest version of the application and will enable high-priority notifications.

In the notification filter expression, it would look like :
```
subject.project.is_latest == true
```

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/main/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

Start with notification/api/src/main/proto/org/dependencytrack/notification/v1/notification.proto at the subject.project definition linked in the issue. Check how notification filter expressions expose project fields, then verify that subject.project.is_latest can be used to select the latest application version and supports the proposed true comparison.

Written by the indexing model from the issue text.