Display publish date (if available) in component details

### Current Behavior

Dependency-Track can retrieve the publish date for components by looking them up in external package repositories like Maven Central.

Currently, the UI only displays a small indicator if a component is not the newest available version. The UI does not currently show the components actual age.

With #398, it will be possible to define policies for component age. This will cause policy violations to be generated whenever a component exceeds a certain age, but users will not be able to see how old the respective components actually are.

### Proposed Behavior

We should display the component age in the UI, given we have this information.

There should probably be a disclaimer that this date reflects when the component was last published or modified, and not necessarily when it was released. If organizations upload legacy libraries to their internal repository, the publish date we get will be misleading.

### 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/frontend/issues) for whether this enhancement was already requested

The issue names no files, tests, or entry points. Start by locating the component-details UI and the existing newest-version indicator, then trace where component publish dates are exposed to the frontend. Done means showing the age when a date is available and adding the proposed disclaimer about last publication or modification.

Written by the indexing model from the issue text.