After the [recent supply chain attack](https://www.wiz.io/blog/new-github-action-supply-chain-attack-reviewdog-action-setup)
in `tj-actions/changed-files` and actions based on it, it's become clear
that relying on git tags to pin our dependencies is not enough (as tags
can simply be replaced). Therefore we need to switch to hashes.
Dependabot should continue to update these dependencies for us.
Best reviewed commit-by-commit. Though if CI passes, we're *probably*
fine.
GitHub appears to be deprecating addProjectNextItem by not allowing it to be used alongside projectV2 to get the project ID, so switching to using addProjectV2ItemById instead.
