Provide search for Java packages within a maven repo and indicate if they are exported or not

[Lambeaux]

Scope

Applies to experiment: https://github.com/connexta/osg-eyes/tree/mvn-indexing

Goal

When resolving feature dependencies and packages are specified in the error messages, it would be really useful to quickly map those packages to actual artifacts, especially since the mapping is not always 1-to-1.

Notes

This could be resolved simply with a new index creator following the pattern here:
https://github.com/apache/maven-indexer/blob/maven-indexer-6.0.0/indexer-core/src/main/java/org/apache/maven/index/creator/JarFileContentsIndexCreator.java#L165-L173

Actual parsing could be delegated to Clojure code if necessary to preserve the vision for a unified set of CLI tools. The repository traversal is fine to remain in Java.

Indicating if the package is exported or not would be trivial - just need to see if the stored exported packages header contains the searched package name for each discovered artifact.