importd: change untar logic to be based on libarchive rather than shelling out to...

importd: change untar logic to be based on libarchive rather than shelling out to gnu tar (#39143)

Let's use libarchive consistently everywhere, both for tarring and
untarring.

Note that there's an existing test case that validates untarring. Now,
it will validate libarchive rather than gnu tar.

Split out of #38728