feat: experiment setting up infra for private vuln feeds

[michaelkedar]

There's growing internal interest in being able to have internal vuln stores.
Set up some terraform configuration to be able to deploy another instance of the vuln pipeline without the website / API.

• Duplicated much of the cluster/database/etc config into a new osv_pipeline module
  • eventually I will add move blocks and remove them from the core osv module to unify this.
• As part of this, created a new service account for the cluster with restricted access (it should have everything it needs)
• Added a new private-osv environment to deploy the infra to oss-vdb-test (for now). This isn't automatically deployed anywhere - I'll run terrform apply when this is ready to merge.