Add zlib support to extractGzip

[egibs]

We've historically had issues extracting zlib-compressed files such as these compressed Pickle files:

time=2024-12-17T07:22:02.609-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py27_np17.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py27_np17.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.610-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py34_np19.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py34_np19.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.610-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py33_np18.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py33_np18.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.610-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py35_np19.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.10.0_compressed_pickle_py35_np19.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.622-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.8.4_compressed_pickle_py27_np17.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.8.4_compressed_pickle_py27_np17.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.623-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py27_np16.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py27_np16.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.623-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py27_np17.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py27_np17.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.623-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py34_np19.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py34_np19.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.624-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py35_np19.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.2_compressed_pickle_py35_np19.gz: failed to create gzip reader: gzip: invalid header"
time=2024-12-17T07:22:02.626-06:00 level=ERROR source=~/repos/chainguard-dev/malcontent/pkg/action/scan.go:330 msg="unable to process ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.4.dev0_compressed_cache_size_pickle_py35_np19.gz: extract to temp: failed to extract ~/Downloads/nemo/usr/share/nemo/.venv/lib/python3.11/site-packages/joblib/test/data/joblib_0.9.4.dev0_compressed_cache_size_pickle_py35_np19.gz: failed to create gzip reader: gzip: invalid header"

Since zlib files don't have a specific extension, I added the functionality to the gzip function since the files we've encountered have had the .gz extension. Ideally, we'd handle this independently of extension but that's for a future PR (probably when I refactor archive.go.)

With these changes:

$ go run cmd/mal/mal.go --all analyze ~/Downloads/nemo/joblib_0.10.0_compressed_pickle_py27_np17.gz
🔎 Scanning "~/Downloads/nemo/joblib_0.10.0_compressed_pickle_py27_np17.gz"