Make "xref" show also references for nested JARs referenced via Bundle-ClassPath

[kwin]

The bnd command xref currently only exposes cross references of classes directly contained in a given JAR, however often bundle JARs contain nested JARs being referenced in Bundle-ClassPath. Those should be examined by xref as well (maybe as opt-in feature).

[chrisrueger]

PR is welcome. If you make it opt-in / configurable I think we can merge it quickly.

[chrisrueger]

@kwin I gave this a try with a little help ;) as I needed something like this too for a project : #7068

Docs: https://bnd.bndtools.org/commands/xref.html#nested-jars

Example

You can test it with current 7.3.0-SNAPSHOT

#  Download current bnd snapshot CLI
curl -L -o biz.aQute.bnd-7.3.0-SNAPSHOT.jar https://bndtools.jfrog.io/artifactory/libs-snapshot/biz/aQute/bnd/biz.aQute.bnd/7.3.0-SNAPSHOT/biz.aQute.bnd-7.3.0-20260129.201731-55.jar

# use with with your custom .jar file e.g. example.jar
java -jar biz.aQute.bnd-7.3.0-SNAPSHOT.jar xref --nested example.jar

I tested it with a fat OSGi jar with a lot of .jars in the Bundle-ClassPath and with --nested I get packages of those jars.