CI: Check that the lockfile is up to date.
For at least one job, run the first cargo run with --locked. This will fail if the lockfile needs updating.
I have verified that this correctly detects this situation: https://gitlab.torproject.org/Diziet/arti/-/pipelines/37692 failed. Now I have rebased this branch onto main to get the fix to Cargo.lock.
Prompted by needing to prepare !482 (merged)