Provide link to GMS Aliases in UI (and API)

This https://public.vulnerablecode.io/vulnerabilities/VCID-yqzv-rncc-aaak?search=CVE-2022-40151
has this `GMS-2022-9109` as an alias but without a link to its upstream which is https://gitlab.com/gitlab-org/security-products/gemnasium-db/-/blob/master/maven/com.thoughtworks.xstream/xstream/GMS-2022-9109.yml
We should provide a link to the alias. If we do not store it, we should store a canonical link to an alias and not rely only on computing these on the fly. For GMS (formerly Gemnasium, acquired by Gitlab) there is no easy URL that we can construct as the GMS-2022-9109.yml is stored under a specific directory tree named after the affected package.