Starting from version 12.12.0, Node.js offers built-in support for translating error stack traces using source maps - learn more here: https://medium.com/@nodejs/source-maps-in-node-js-482872b56116

Let's rework @loopback/build to use this new feature on recent version of Node.js, instead of source-map-support module.

If it's possible, then implement a fallback to npm module `source-map-s

Coordinate with #1133 and #1137

Description of issue or feature request:
For consistent use of OOP we should provide classes for all complex metadata fields
and not only for the outer metadata signature wrapper and the inner signed metadata.

This would make the used metadata format more explicit and might have a positive effect on metadata schema validation (see discussion in #1130)

Currently the DTD is not valid for the new item-submission.xml format. https://jira.lyrasis.org/browse/DS-4264

Some packages may bundle dependencies. We could report outdatedness for these the following way: for outdated packages with single download, propagate outdated status onto the download URL. Then we could show this download specially for other packages, or even make it affect the status.