Fix metrics (#618)
* chore: 🤖 prepare the tools to allow overridding the tests
* fix: 🐛 use PROMETHEUS_MULTIPROC_DIR instead of custom env var
The python prometheus client requirest the PROMETHEUS_MULTIPROC_DIR env
var. See
https://github.com/prometheus/client_python#multiprocess-mode-eg-gunicorn.
Also: handle the metrics globally, they cannot be initialized twice.
* ci: 🎡 fix github actions
see
https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/
* ci: 🎡 fix ci
* ci: 🎡 try again to fix the ci
* ci: 🎡 new attempt to fix the ci
* feat: 🎸 update docker images
* style: 💄 fix json format
* fix: 🐛 use PROMETHEUS_MULTIPROC_DIR instead of the previous var
* test: 💍 test /admin/metrics with two workers
* ci: 🎡 fix github action
* style: 💄 fix style
* test: 💍 fix e2e tests
* test: 💍 fix e2e test
* test: 💍 fix e2e test
* test: 💍 fix e2e test
* feat: 🎸 update docker images
* test: 💍 fix e2e tests
* fix: 🐛 fix docker image
* feat: 🎸 increase a bit the default number of splits/ replicas
* ci: 🎡 upgrade actions to fix warnings
