AbstractAggregatingHandler is unfinished

### Affected version

HEAD

### Bug description

resolve the FIXME one way or another

```
@Override
public void finalizeArchiveCreation(final Archiver archiver) {
// this will prompt the isSelected() call, below, for all resources added to the archive.
// FIXME: This needs to be corrected in the AbstractArchiver, where
// runArchiveFinalizers() is called before regular resources are added...
// which is done because the manifest needs to be added first, and the
// manifest-creation component is a finalizer in the assembly plugin...
for (final ResourceIterator it = archiver.getResources(); it.hasNext(); ) {
it.next();
}

addToArchive(archiver);
}
```

Start with AbstractAggregatingHandler and the finalizeArchiveCreation method shown in the issue. Read AbstractArchiver and its runArchiveFinalizers flow, especially how the manifest-creation component is ordered relative to regular resources. Done means the FIXME is resolved without requiring the current resource iteration workaround, with relevant tests or assembly-plugin behavior confirming archive creation remains correct.

Written by the indexing model from the issue text.