Rendering multiple Subtrees in dependency tree tab of Dependency tracker

### Current Behavior

WRT a discussion regarding an issue in cyclonedx-cdxgen https://github.com/CycloneDX/cdxgen/issues/247#issuecomment-1452233031
Currently Dependency tracker only supports displaying one tree in the dependency tree section.

So for a given project the tree is displayed as
```
C
/
A -> B
\
D
```
But many repositories that are analyzed contain multiple trees, i.e. for example if a repository has front-end and back-end
then the trees would not be connected with each other as they do not share dependencies.

### Proposed Behavior

I propose that there is a feature in dependency track to render multiple trees,
So for example if a project has front-end and back-end or more sub-projects as part of it

the trees can be rendered as below
```
C
/
front-end-> B
\
D
back-end -> F -> G -> H

CLI -> A -> B -> C
```
Therefore displaying multiple roots if there are multiple dependency trees in a project.

### 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