Use plexus-utils instead of Maven Shared Utils

Despite what is written in https://maven.apache.org/shared/maven-shared-utils/

This project aims to be a functional replacement for plexus-utils in Maven.

It is not a 100% API compatible replacement though but a replacement with improvements: lots of methods got cleaned up, generics got added and we dropped a lot of unused code.

Then there are additions, like styled message API.

the library is not really well maintained and mostly contains deprecated code now. Plexus-utils nowadays seems to be the better choice (https://lists.apache.org/thread/7dsyg3q1f2qvgzxq3snkcsnfkwltcfwj, and https://the-asf.slack.com/archives/C7Q9JB404/p1654722485674189).

Therefore the changes from JCRVLT-501 should basically be reverted, so that we can get rid of maven-shared-utils (and therefore reduce the dependency footprint of the plugin, as plexus-utils is transitively required anyways).