Uncompress support '.tar.zst' extension and 'application/zstd' mime type.
Add zstandard support to tarball.py for unpacking 'tar.zst' file archives. It requires 'zstandard' python package as a dependency. It may require 'zstd' package on host.
Zstandard support is required by the archlinux loader.
Test Plan
Add archive example file and a test for unpacking zst file.
Migrated from D7993 (view on Phabricator)