Add statsd as a dependency to our setup

This path adds statsd as a dependency loaded with pipy to ship into our production environment. It's needed for Airflow to send metrics to stasd-exporter, and then Prometheus.

In extra, with this patch, we are:

• adding security fixes from Airflow (bump to 2.7.3 from 2.6.3)
• updating the dependency list
• loading graphviz from pipy in place of conda-forge to make the bundle platform agnostic

Bug: T349532

Bug: T343232

According to a discussion with the RelEng team, it seems like we can't build an image with a Dockerfile anymore (only Blubber allowed).

This breaks our current pipeline.

In this patch, I implement a temporary (?) workaround where we rebuild the whole environment at the beginning of each run.

Bug: T351792