It is no longer public (or even private) API. BPackageDataReaderFactory
returns a BAbstractBufferedDataReader instead. The advantage is that
the latter doesn't have hpkg format specific dependencies.
It uses sub-namespace BPackage::BHPKG::V1. Unlike the one for the
current format version, the V1 version of BPackageInfoContentHandler
lives in BHPKG(::V1) sub-namespace and is private.