`bench-deploy`: Convert between Criterion JSON formats

After #44

Currently, our `gh-pages` benchmark JSONs can't be used with `criterion-table` and our `commit-comment` benchmarks can't be used in plots. After some testing I've found that reformatting the JSON files is fairly straightforward using `jq`. This would have several benefits:
- Run only one benchmark per commit, rather than fiddling with env vars to produce several for use in our various comparison tools. This saves time and UX hassle
- Cached `commit-comment` benchmarks could be immediately deployed when a PR is merged, rather than having to re-run the benchmark in the `gh-pages` format for plotting & deployment. This saves time, runner resources and clutter in `gh-pages`

Verfolge die bestehenden gh-pages- und commit-comment-Benchmark-Workflow-Pfade und prüfe die von ihnen erzeugten Criterion-JSON-Formate. Verwende jq, um die Konvertierung zwischen diesen Formaten zu definieren, und verifiziere anschließend, dass ein Benchmark pro Commit criterion-table, Plots und Deployment ohne separate erneute Ausführungen unterstützen kann.

Vom Indexierungsmodell aus dem Issue-Text verfasst.