Reconsider criteria to align with GHSA

[djc]

In #1808, it became clear that at least two separate people (one of which was me) got confused by the fact that a GHSA was issued for rustix without a RustSec advisory being published. The maintainer made a (convincing) argument that the issue didn't meet the RustSec criteria. IMO it's unfortunate if the RustSec advisory database is "incomplete" in that issues for which GHSAs were filed are not included.

Opening this issue to discuss what could be done about this.

[tarcieri]

It's a tricky question. If something like rustsec/rustsec#656 were to ship, I'm curious how practical manual curation based on our current polices would actually be

cc @amousset