Set published date to issued date in OSV data

[andrewpollock]

Hello,

@jayvdb reported google/osv.dev#2843 to OSV.dev, but it's really an issue with the source data as published in the RUST Advisory Database, so I wanted to have the discussion on an issue here.

[tarcieri]

The only place we currently collect this information is in the git history at the time advisories are issued a RUSTSEC ID.

Perhaps we can add a field for it and start collecting it explicitly.

[Shnatsel]

We could make the ID assigner fill in the date. That would be more robust and also less work for the maintainers.