## Problem
Docker Hub has new rate limits coming up, and to avoid problems coming
with those we're switching to GHCR.
## Summary of changes
- Push images to GHCR initially and distribute them from there
- Use images from GHCR in docker-compose
## Problem
Pinging groups on slack didn't work, because I didn't use the correct
syntax.
## Summary of changes
Use the correct syntax for pinging groups.
## Problem
There are two (related) problems with the previous handling of
`cargo-deny`:
- When a new advisory is added to rustsec that affects a dependency,
unrelated pull requests will fail.
- New advisories rely on pushes or PRs to be surfaced. Problems that
already exist on main will only be found if we try to merge new things
into main.
## Summary of changes
We split out `cargo-deny` into a separate workflow that runs on all PRs
that touch `Cargo.lock`, and on a schedule on `main`, `release`,
`release-compute` and `release-proxy` to find new advisories.