Proper feedback on BOM upload

### Current Behavior

When uploading a BOM via the v1/bom endpoint, the user is given a "#/definitions/BomUploadResponse" containing a token as response.
This token can then be used in order to query the current processing status via the v1/bom/token/{uuid} endpoint. It only gives a boolean result though - either the BOM is currently being processed - or it isn't.

When uploading a BOM, a lot of stuff can go wrong though - leading to either no project being created - or even incomplete projects within DependencyTrack without any feedback to the user about any of those error states. The only possibility to see that (and what) something went wrong is to look at the server logs - which aren't accessible to the user.
See issues for examples:
https://github.com/DependencyTrack/dependency-track/issues/3371
https://github.com/DependencyTrack/dependency-track/issues/3324
https://github.com/DependencyTrack/dependency-track/issues/3274
https://github.com/DependencyTrack/dependency-track/issues/3081
https://github.com/DependencyTrack/dependency-track/issues/2821
... and more.

### Proposed Behavior

The v1/bom/token/{uuid} endpoint shall include information about any errors encountered during the processing of a BOM. This includes stuff like "wrong format" - but also any exception that happened during processing.

### 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