ROX-13435: fix RHELv2 updates

[RTann]

The changes relating to the diff step in #928 caused RHELv2 updates to not work properly with older Scanner versions.

Older Scanner versions rely on PackageInfos to be populated. Genesis dumps no longer populate this field, and the diff converted each base dump's PackageInfos to Packages. Instead, we should have converted the new Packages to the old PackageInfos so older scanners would understand them properly.

Local Testing Steps:

1. Run make build-updater
2. Run ./bin/updater generate-dump --out-file test.zip. This will generate the latest genesis dump with the latest vulnerabilities
3. Run ./test.sh where test.sh is defined below
4. Confirm PackageInfos are populated the correct data. For example, you can unzip /tmp/diff-dumps/dump0/diff.zip and look at rhelv2/vulns/RHEL9-rhel-9-including-unpatched.json and verify "RHSA-2022:7288" has all the fields populated as expected

test.sh:

mkdir -p /tmp/diff-dumps
idx=-1
while IFS=$'\t' read -r dumploc timestamp config; do
    idx=$((idx+1))
    dump_file_name="${dumploc##*/}"
    echo "Pulling genesis dump from ${dumploc}"
    gsutil cp "${dumploc}" .
    timestamp_in_zip="$(unzip -p "${dump_file_name}" manifest.json | jq -r '.until')"
    echo "Got timestamps -- from zip: ${timestamp_in_zip}; from manifest: ${timestamp}"
    [[ "${timestamp_in_zip}" == "${timestamp}" ]] # Assertion on the manifest contents
    # $ROOT/bin/updater is from the generate-genesis image in OpenShift CI.
    ./bin/updater diff-dumps --base-dump "${dump_file_name}" --head-dump test.zip --config "${config}" --out-file "/tmp/diff-dumps/dump${idx}/diff.zip"
done < <(jq -r '.knownGenesisDumps | .[]| [.dumpLocationInGS, .timestamp, (.config // empty | tostring)] | @tsv' < test.json)
du -d 2 -kh "/tmp/diff-dumps"

test.json:

{
  "knownGenesisDumps": [
    {
      "dumpLocationInGS": "gs://stackrox-scanner-ci-vuln-dump/genesis-20220908183429.zip",
      "timestamp": "2022-09-08T18:34:29.343211144Z",
      "uuid": "f81dbc6b-5899-433b-bc86-9127219a9d89",
      "config": {
        "useLegacyRHELv2PackageInfos": true,
        "ignoreIstioVulns": true
      }
    }
  ]
}

[ghost]

Images are ready for the commit at c19904a.

To use the images, use the tag 2.26.x-24-gc19904ac62.