Allow attaching the shaded artifact as primary one while keeping the original one as secondary one.

### New feature, improvement proposal

With the parameter [`shadedArtifactAttached`](https://maven.apache.org/plugins/maven-shade-plugin/shade-mojo.html#shadedArtifactAttached) it is possible to keep the original artifact as main artifact, however it would be beneficial to instead make the original one a secondary artifact while having the shared artifact become the main one.

Start with the Maven Shade Plugin documentation for `shadedArtifactAttached` and trace the plugin’s artifact-selection behavior. Define how the shaded artifact becomes primary while the original becomes secondary, then verify the resulting Maven artifacts and document or test the new behavior.

Written by the indexing model from the issue text.