Pin Depot runners to Ubuntu 24.04 (#27656)
## Summary
Previously, our Depot-backed CI and release jobs used floating Ubuntu
runner labels. We now pin the four-core release runners and eight-core
CI runners to Ubuntu 24.04, update actionlint accordingly, and keep the
cargo-dist runner configuration aligned with the generated release
workflow.
The existing release approval gate and checksum-verified cargo-dist
installation remain unchanged.
