user added components shall not be deleted after SBOM import

### Current Behavior

When one manually adds a component and then uploads an SBOM the manually added components are deleted.

### Proposed Behavior

Do not delete manually added coponents after SBOM import or at least flag them as manually added so one can back them up over the API

### 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