Enhance Defectdojo and other integrations to only sync on changes

### Current Behavior

Currently the syncing to Defectdojo is managed over the "Synchronization cadence" variable regardless if the findings in a project have changed, this leads to a lot of imports(or re-imports) into Defectdojo.

### Proposed Behavior

The VulnerabilityManagementUploadTask stores a unique value that identifies the current set of findings on a project. This could be "ProjectMetrics" or a HASH of the current Finding_ids (and status ?), at least something that we know will change if the findings within a project change.

Only when this unique value has changed (and therefore the findings within the project have changed) the findings are synced to Defectdojo again.

### 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