malcontent's nested archive extraction failure can drop content from scan inputs

malcontent is software for discovering supply-chain compromises through context, differential analysis, and YARA. Prior to version 1.21.0, malcontent would remove nested archives which failed to extract which could potentially leave malicious content. A better approach is to preserve these archives so that malcontent can attempt a best-effort scan of the archive bytes. Version 1.21.0 fixes the issue.