Allow /api/v1/project/lookup to return project with no version

### Current Behavior

Using the /api/v1/project/lookup?name=x&version=y allows looking up a project with a version.
However, if a project does have an empty version field, this API cannot be used (as version is required parameter) and there is no equivalent API to return projects without version.

### Proposed Behavior

Allow the lookup API to look up projects with no version.

Consideration:
It might be misleading if only searching for name does not return all projects with that name, so docs would have to make this clear, that not providing version is only returning a project with this name and no version.

### 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