Return a hash (or hash reference, depending on context) for the given
package.
PACK may either be an AptPkg::Cache::VerFile object, an
AptPkg::Cache::DescFile object or a package name.
The hash contains the following keys:
FileName, Checksum-FileSize, MD5Hash, SHA256, SourcePkg,
Maintainer, ShortDesc, LongDesc and Name.
with values taken from the packages or translation file.
Note that LongDesc is generally not useful for AptPkg::Cache::VerFile
objects, which refer to the Packages file, as these no longer contain the full
description (now in the Translation files).
If PACK is a package name, these additional values are set:
Section and VerStr.
and the following values are overridden with the translated versions:
ShortDesc and LongDesc.